Current File : //proc/thread-self/root/opt/imunify360/venv/lib64/python3.11/site-packages/aiohttp/helpers.py
"""Various helper functions"""
import asyncio
import base64
import binascii
import datetime
import functools
import inspect
import netrc
import os
import platform
import re
import sys
import time
import warnings
import weakref
from collections import namedtuple
from contextlib import suppress
from email.parser import HeaderParser
from email.utils import parsedate
from math import ceil
from pathlib import Path
from types import TracebackType
from typing import (
Any,
Callable,
ContextManager,
Dict,
Generator,
Generic,
Iterable,
Iterator,
List,
Mapping,
Optional,
Pattern,
Set,
Tuple,
Type,
TypeVar,
Union,
cast,
)
from urllib.parse import quote
from urllib.request import getproxies, proxy_bypass
import async_timeout
import attr
from multidict import MultiDict, MultiDictProxy
from yarl import URL
from . import hdrs
from .log import client_logger, internal_logger
from .typedefs import PathLike, Protocol # noqa
__all__ = ("BasicAuth", "ChainMapProxy", "ETag")
IS_MACOS = platform.system() == "Darwin"
IS_WINDOWS = platform.system() == "Windows"
PY_36 = sys.version_info >= (3, 6)
PY_37 = sys.version_info >= (3, 7)
PY_38 = sys.version_info >= (3, 8)
PY_310 = sys.version_info >= (3, 10)
PY_311 = sys.version_info >= (3, 11)
if sys.version_info < (3, 7):
import idna_ssl
idna_ssl.patch_match_hostname()
def all_tasks(
loop: Optional[asyncio.AbstractEventLoop] = None,
) -> Set["asyncio.Task[Any]"]:
tasks = list(asyncio.Task.all_tasks(loop))
return {t for t in tasks if not t.done()}
else:
all_tasks = asyncio.all_tasks
_T = TypeVar("_T")
_S = TypeVar("_S")
sentinel: Any = object()
NO_EXTENSIONS: bool = bool(os.environ.get("AIOHTTP_NO_EXTENSIONS"))
# N.B. sys.flags.dev_mode is available on Python 3.7+, use getattr
# for compatibility with older versions
DEBUG: bool = getattr(sys.flags, "dev_mode", False) or (
not sys.flags.ignore_environment and bool(os.environ.get("PYTHONASYNCIODEBUG"))
)
CHAR = {chr(i) for i in range(0, 128)}
CTL = {chr(i) for i in range(0, 32)} | {
chr(127),
}
SEPARATORS = {
"(",
")",
"<",
">",
"@",
",",
";",
":",
"\\",
'"',
"/",
"[",
"]",
"?",
"=",
"{",
"}",
" ",
chr(9),
}
TOKEN = CHAR ^ CTL ^ SEPARATORS
class noop:
def __await__(self) -> Generator[None, None, None]:
yield
class BasicAuth(namedtuple("BasicAuth", ["login", "password", "encoding"])):
"""Http basic authentication helper."""
def __new__(
cls, login: str, password: str = "", encoding: str = "latin1"
) -> "BasicAuth":
if login is None:
raise ValueError("None is not allowed as login value")
if password is None:
raise ValueError("None is not allowed as password value")
if ":" in login:
raise ValueError('A ":" is not allowed in login (RFC 1945#section-11.1)')
return super().__new__(cls, login, password, encoding)
@classmethod
def decode(cls, auth_header: str, encoding: str = "latin1") -> "BasicAuth":
"""Create a BasicAuth object from an Authorization HTTP header."""
try:
auth_type, encoded_credentials = auth_header.split(" ", 1)
except ValueError:
raise ValueError("Could not parse authorization header.")
if auth_type.lower() != "basic":
raise ValueError("Unknown authorization method %s" % auth_type)
try:
decoded = base64.b64decode(
encoded_credentials.encode("ascii"), validate=True
).decode(encoding)
except binascii.Error:
raise ValueError("Invalid base64 encoding.")
try:
# RFC 2617 HTTP Authentication
# https://www.ietf.org/rfc/rfc2617.txt
# the colon must be present, but the username and password may be
# otherwise blank.
username, password = decoded.split(":", 1)
except ValueError:
raise ValueError("Invalid credentials.")
return cls(username, password, encoding=encoding)
@classmethod
def from_url(cls, url: URL, *, encoding: str = "latin1") -> Optional["BasicAuth"]:
"""Create BasicAuth from url."""
if not isinstance(url, URL):
raise TypeError("url should be yarl.URL instance")
if url.user is None:
return None
return cls(url.user, url.password or "", encoding=encoding)
def encode(self) -> str:
"""Encode credentials."""
creds = (f"{self.login}:{self.password}").encode(self.encoding)
return "Basic %s" % base64.b64encode(creds).decode(self.encoding)
def strip_auth_from_url(url: URL) -> Tuple[URL, Optional[BasicAuth]]:
auth = BasicAuth.from_url(url)
if auth is None:
return url, None
else:
return url.with_user(None), auth
def netrc_from_env() -> Optional[netrc.netrc]:
"""Load netrc from file.
Attempt to load it from the path specified by the env-var
NETRC or in the default location in the user's home directory.
Returns None if it couldn't be found or fails to parse.
"""
netrc_env = os.environ.get("NETRC")
if netrc_env is not None:
netrc_path = Path(netrc_env)
else:
try:
home_dir = Path.home()
except RuntimeError as e: # pragma: no cover
# if pathlib can't resolve home, it may raise a RuntimeError
client_logger.debug(
"Could not resolve home directory when "
"trying to look for .netrc file: %s",
e,
)
return None
netrc_path = home_dir / ("_netrc" if IS_WINDOWS else ".netrc")
try:
return netrc.netrc(str(netrc_path))
except netrc.NetrcParseError as e:
client_logger.warning("Could not parse .netrc file: %s", e)
except OSError as e:
# we couldn't read the file (doesn't exist, permissions, etc.)
if netrc_env or netrc_path.is_file():
# only warn if the environment wanted us to load it,
# or it appears like the default file does actually exist
client_logger.warning("Could not read .netrc file: %s", e)
return None
@attr.s(auto_attribs=True, frozen=True, slots=True)
class ProxyInfo:
proxy: URL
proxy_auth: Optional[BasicAuth]
def proxies_from_env() -> Dict[str, ProxyInfo]:
proxy_urls = {
k: URL(v)
for k, v in getproxies().items()
if k in ("http", "https", "ws", "wss")
}
netrc_obj = netrc_from_env()
stripped = {k: strip_auth_from_url(v) for k, v in proxy_urls.items()}
ret = {}
for proto, val in stripped.items():
proxy, auth = val
if proxy.scheme in ("https", "wss"):
client_logger.warning(
"%s proxies %s are not supported, ignoring", proxy.scheme.upper(), proxy
)
continue
if netrc_obj and auth is None:
auth_from_netrc = None
if proxy.host is not None:
auth_from_netrc = netrc_obj.authenticators(proxy.host)
if auth_from_netrc is not None:
# auth_from_netrc is a (`user`, `account`, `password`) tuple,
# `user` and `account` both can be username,
# if `user` is None, use `account`
*logins, password = auth_from_netrc
login = logins[0] if logins[0] else logins[-1]
auth = BasicAuth(cast(str, login), cast(str, password))
ret[proto] = ProxyInfo(proxy, auth)
return ret
def current_task(
loop: Optional[asyncio.AbstractEventLoop] = None,
) -> "Optional[asyncio.Task[Any]]":
if sys.version_info >= (3, 7):
return asyncio.current_task(loop=loop)
else:
return asyncio.Task.current_task(loop=loop)
def get_running_loop(
loop: Optional[asyncio.AbstractEventLoop] = None,
) -> asyncio.AbstractEventLoop:
if loop is None:
loop = asyncio.get_event_loop()
if not loop.is_running():
warnings.warn(
"The object should be created within an async function",
DeprecationWarning,
stacklevel=3,
)
if loop.get_debug():
internal_logger.warning(
"The object should be created within an async function", stack_info=True
)
return loop
def isasyncgenfunction(obj: Any) -> bool:
func = getattr(inspect, "isasyncgenfunction", None)
if func is not None:
return func(obj) # type: ignore[no-any-return]
else:
return False
def get_env_proxy_for_url(url: URL) -> Tuple[URL, Optional[BasicAuth]]:
"""Get a permitted proxy for the given URL from the env."""
if url.host is not None and proxy_bypass(url.host):
raise LookupError(f"Proxying is disallowed for `{url.host!r}`")
proxies_in_env = proxies_from_env()
try:
proxy_info = proxies_in_env[url.scheme]
except KeyError:
raise LookupError(f"No proxies found for `{url!s}` in the env")
else:
return proxy_info.proxy, proxy_info.proxy_auth
@attr.s(auto_attribs=True, frozen=True, slots=True)
class MimeType:
type: str
subtype: str
suffix: str
parameters: "MultiDictProxy[str]"
@functools.lru_cache(maxsize=56)
def parse_mimetype(mimetype: str) -> MimeType:
"""Parses a MIME type into its components.
mimetype is a MIME type string.
Returns a MimeType object.
Example:
>>> parse_mimetype('text/html; charset=utf-8')
MimeType(type='text', subtype='html', suffix='',
parameters={'charset': 'utf-8'})
"""
if not mimetype:
return MimeType(
type="", subtype="", suffix="", parameters=MultiDictProxy(MultiDict())
)
parts = mimetype.split(";")
params: MultiDict[str] = MultiDict()
for item in parts[1:]:
if not item:
continue
key, value = cast(
Tuple[str, str], item.split("=", 1) if "=" in item else (item, "")
)
params.add(key.lower().strip(), value.strip(' "'))
fulltype = parts[0].strip().lower()
if fulltype == "*":
fulltype = "*/*"
mtype, stype = (
cast(Tuple[str, str], fulltype.split("/", 1))
if "/" in fulltype
else (fulltype, "")
)
stype, suffix = (
cast(Tuple[str, str], stype.split("+", 1)) if "+" in stype else (stype, "")
)
return MimeType(
type=mtype, subtype=stype, suffix=suffix, parameters=MultiDictProxy(params)
)
def guess_filename(obj: Any, default: Optional[str] = None) -> Optional[str]:
name = getattr(obj, "name", None)
if name and isinstance(name, str) and name[0] != "<" and name[-1] != ">":
return Path(name).name
return default
not_qtext_re = re.compile(r"[^\041\043-\133\135-\176]")
QCONTENT = {chr(i) for i in range(0x20, 0x7F)} | {"\t"}
def quoted_string(content: str) -> str:
"""Return 7-bit content as quoted-string.
Format content into a quoted-string as defined in RFC5322 for
Internet Message Format. Notice that this is not the 8-bit HTTP
format, but the 7-bit email format. Content must be in usascii or
a ValueError is raised.
"""
if not (QCONTENT > set(content)):
raise ValueError(f"bad content for quoted-string {content!r}")
return not_qtext_re.sub(lambda x: "\\" + x.group(0), content)
def content_disposition_header(
disptype: str, quote_fields: bool = True, _charset: str = "utf-8", **params: str
) -> str:
"""Sets ``Content-Disposition`` header for MIME.
This is the MIME payload Content-Disposition header from RFC 2183
and RFC 7579 section 4.2, not the HTTP Content-Disposition from
RFC 6266.
disptype is a disposition type: inline, attachment, form-data.
Should be valid extension token (see RFC 2183)
quote_fields performs value quoting to 7-bit MIME headers
according to RFC 7578. Set to quote_fields to False if recipient
can take 8-bit file names and field values.
_charset specifies the charset to use when quote_fields is True.
params is a dict with disposition params.
"""
if not disptype or not (TOKEN > set(disptype)):
raise ValueError("bad content disposition type {!r}" "".format(disptype))
value = disptype
if params:
lparams = []
for key, val in params.items():
if not key or not (TOKEN > set(key)):
raise ValueError(
"bad content disposition parameter" " {!r}={!r}".format(key, val)
)
if quote_fields:
if key.lower() == "filename":
qval = quote(val, "", encoding=_charset)
lparams.append((key, '"%s"' % qval))
else:
try:
qval = quoted_string(val)
except ValueError:
qval = "".join(
(_charset, "''", quote(val, "", encoding=_charset))
)
lparams.append((key + "*", qval))
else:
lparams.append((key, '"%s"' % qval))
else:
qval = val.replace("\\", "\\\\").replace('"', '\\"')
lparams.append((key, '"%s"' % qval))
sparams = "; ".join("=".join(pair) for pair in lparams)
value = "; ".join((value, sparams))
return value
class _TSelf(Protocol, Generic[_T]):
_cache: Dict[str, _T]
class reify(Generic[_T]):
"""Use as a class method decorator.
It operates almost exactly like
the Python `@property` decorator, but it puts the result of the
method it decorates into the instance dict after the first call,
effectively replacing the function it decorates with an instance
variable. It is, in Python parlance, a data descriptor.
"""
def __init__(self, wrapped: Callable[..., _T]) -> None:
self.wrapped = wrapped
self.__doc__ = wrapped.__doc__
self.name = wrapped.__name__
def __get__(self, inst: _TSelf[_T], owner: Optional[Type[Any]] = None) -> _T:
try:
try:
return inst._cache[self.name]
except KeyError:
val = self.wrapped(inst)
inst._cache[self.name] = val
return val
except AttributeError:
if inst is None:
return self
raise
def __set__(self, inst: _TSelf[_T], value: _T) -> None:
raise AttributeError("reified property is read-only")
reify_py = reify
try:
from ._helpers import reify as reify_c
if not NO_EXTENSIONS:
reify = reify_c # type: ignore[misc,assignment]
except ImportError:
pass
_ipv4_pattern = (
r"^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}"
r"(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$"
)
_ipv6_pattern = (
r"^(?:(?:(?:[A-F0-9]{1,4}:){6}|(?=(?:[A-F0-9]{0,4}:){0,6}"
r"(?:[0-9]{1,3}\.){3}[0-9]{1,3}$)(([0-9A-F]{1,4}:){0,5}|:)"
r"((:[0-9A-F]{1,4}){1,5}:|:)|::(?:[A-F0-9]{1,4}:){5})"
r"(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.){3}"
r"(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])|(?:[A-F0-9]{1,4}:){7}"
r"[A-F0-9]{1,4}|(?=(?:[A-F0-9]{0,4}:){0,7}[A-F0-9]{0,4}$)"
r"(([0-9A-F]{1,4}:){1,7}|:)((:[0-9A-F]{1,4}){1,7}|:)|(?:[A-F0-9]{1,4}:){7}"
r":|:(:[A-F0-9]{1,4}){7})$"
)
_ipv4_regex = re.compile(_ipv4_pattern)
_ipv6_regex = re.compile(_ipv6_pattern, flags=re.IGNORECASE)
_ipv4_regexb = re.compile(_ipv4_pattern.encode("ascii"))
_ipv6_regexb = re.compile(_ipv6_pattern.encode("ascii"), flags=re.IGNORECASE)
def _is_ip_address(
regex: Pattern[str], regexb: Pattern[bytes], host: Optional[Union[str, bytes]]
) -> bool:
if host is None:
return False
if isinstance(host, str):
return bool(regex.match(host))
elif isinstance(host, (bytes, bytearray, memoryview)):
return bool(regexb.match(host))
else:
raise TypeError(f"{host} [{type(host)}] is not a str or bytes")
is_ipv4_address = functools.partial(_is_ip_address, _ipv4_regex, _ipv4_regexb)
is_ipv6_address = functools.partial(_is_ip_address, _ipv6_regex, _ipv6_regexb)
def is_ip_address(host: Optional[Union[str, bytes, bytearray, memoryview]]) -> bool:
return is_ipv4_address(host) or is_ipv6_address(host)
def next_whole_second() -> datetime.datetime:
"""Return current time rounded up to the next whole second."""
return datetime.datetime.now(datetime.timezone.utc).replace(
microsecond=0
) + datetime.timedelta(seconds=0)
_cached_current_datetime: Optional[int] = None
_cached_formatted_datetime = ""
def rfc822_formatted_time() -> str:
global _cached_current_datetime
global _cached_formatted_datetime
now = int(time.time())
if now != _cached_current_datetime:
# Weekday and month names for HTTP date/time formatting;
# always English!
# Tuples are constants stored in codeobject!
_weekdayname = ("Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun")
_monthname = (
"", # Dummy so we can use 1-based month numbers
"Jan",
"Feb",
"Mar",
"Apr",
"May",
"Jun",
"Jul",
"Aug",
"Sep",
"Oct",
"Nov",
"Dec",
)
year, month, day, hh, mm, ss, wd, *tail = time.gmtime(now)
_cached_formatted_datetime = "%s, %02d %3s %4d %02d:%02d:%02d GMT" % (
_weekdayname[wd],
day,
_monthname[month],
year,
hh,
mm,
ss,
)
_cached_current_datetime = now
return _cached_formatted_datetime
def _weakref_handle(info: "Tuple[weakref.ref[object], str]") -> None:
ref, name = info
ob = ref()
if ob is not None:
with suppress(Exception):
getattr(ob, name)()
def weakref_handle(
ob: object, name: str, timeout: float, loop: asyncio.AbstractEventLoop
) -> Optional[asyncio.TimerHandle]:
if timeout is not None and timeout > 0:
when = loop.time() + timeout
if timeout >= 5:
when = ceil(when)
return loop.call_at(when, _weakref_handle, (weakref.ref(ob), name))
return None
def call_later(
cb: Callable[[], Any], timeout: float, loop: asyncio.AbstractEventLoop
) -> Optional[asyncio.TimerHandle]:
if timeout is not None and timeout > 0:
when = loop.time() + timeout
if timeout > 5:
when = ceil(when)
return loop.call_at(when, cb)
return None
class TimeoutHandle:
"""Timeout handle"""
def __init__(
self, loop: asyncio.AbstractEventLoop, timeout: Optional[float]
) -> None:
self._timeout = timeout
self._loop = loop
self._callbacks: List[
Tuple[Callable[..., None], Tuple[Any, ...], Dict[str, Any]]
] = []
def register(
self, callback: Callable[..., None], *args: Any, **kwargs: Any
) -> None:
self._callbacks.append((callback, args, kwargs))
def close(self) -> None:
self._callbacks.clear()
def start(self) -> Optional[asyncio.Handle]:
timeout = self._timeout
if timeout is not None and timeout > 0:
when = self._loop.time() + timeout
if timeout >= 5:
when = ceil(when)
return self._loop.call_at(when, self.__call__)
else:
return None
def timer(self) -> "BaseTimerContext":
if self._timeout is not None and self._timeout > 0:
timer = TimerContext(self._loop)
self.register(timer.timeout)
return timer
else:
return TimerNoop()
def __call__(self) -> None:
for cb, args, kwargs in self._callbacks:
with suppress(Exception):
cb(*args, **kwargs)
self._callbacks.clear()
class BaseTimerContext(ContextManager["BaseTimerContext"]):
pass
class TimerNoop(BaseTimerContext):
def __enter__(self) -> BaseTimerContext:
return self
def __exit__(
self,
exc_type: Optional[Type[BaseException]],
exc_val: Optional[BaseException],
exc_tb: Optional[TracebackType],
) -> None:
return
class TimerContext(BaseTimerContext):
"""Low resolution timeout context manager"""
def __init__(self, loop: asyncio.AbstractEventLoop) -> None:
self._loop = loop
self._tasks: List[asyncio.Task[Any]] = []
self._cancelled = False
def __enter__(self) -> BaseTimerContext:
task = current_task(loop=self._loop)
if task is None:
raise RuntimeError(
"Timeout context manager should be used " "inside a task"
)
if self._cancelled:
raise asyncio.TimeoutError from None
self._tasks.append(task)
return self
def __exit__(
self,
exc_type: Optional[Type[BaseException]],
exc_val: Optional[BaseException],
exc_tb: Optional[TracebackType],
) -> Optional[bool]:
if self._tasks:
self._tasks.pop()
if exc_type is asyncio.CancelledError and self._cancelled:
raise asyncio.TimeoutError from None
return None
def timeout(self) -> None:
if not self._cancelled:
for task in set(self._tasks):
task.cancel()
self._cancelled = True
def ceil_timeout(delay: Optional[float]) -> async_timeout.Timeout:
if delay is None or delay <= 0:
return async_timeout.timeout(None)
loop = get_running_loop()
now = loop.time()
when = now + delay
if delay > 5:
when = ceil(when)
return async_timeout.timeout_at(when)
class HeadersMixin:
ATTRS = frozenset(["_content_type", "_content_dict", "_stored_content_type"])
_content_type: Optional[str] = None
_content_dict: Optional[Dict[str, str]] = None
_stored_content_type = sentinel
def _parse_content_type(self, raw: str) -> None:
self._stored_content_type = raw
if raw is None:
# default value according to RFC 2616
self._content_type = "application/octet-stream"
self._content_dict = {}
else:
msg = HeaderParser().parsestr("Content-Type: " + raw)
self._content_type = msg.get_content_type()
params = msg.get_params()
self._content_dict = dict(params[1:]) # First element is content type again
@property
def content_type(self) -> str:
"""The value of content part for Content-Type HTTP header."""
raw = self._headers.get(hdrs.CONTENT_TYPE) # type: ignore[attr-defined]
if self._stored_content_type != raw:
self._parse_content_type(raw)
return self._content_type # type: ignore[return-value]
@property
def charset(self) -> Optional[str]:
"""The value of charset part for Content-Type HTTP header."""
raw = self._headers.get(hdrs.CONTENT_TYPE) # type: ignore[attr-defined]
if self._stored_content_type != raw:
self._parse_content_type(raw)
return self._content_dict.get("charset") # type: ignore[union-attr]
@property
def content_length(self) -> Optional[int]:
"""The value of Content-Length HTTP header."""
content_length = self._headers.get( # type: ignore[attr-defined]
hdrs.CONTENT_LENGTH
)
if content_length is not None:
return int(content_length)
else:
return None
def set_result(fut: "asyncio.Future[_T]", result: _T) -> None:
if not fut.done():
fut.set_result(result)
def set_exception(fut: "asyncio.Future[_T]", exc: BaseException) -> None:
if not fut.done():
fut.set_exception(exc)
class ChainMapProxy(Mapping[str, Any]):
__slots__ = ("_maps",)
def __init__(self, maps: Iterable[Mapping[str, Any]]) -> None:
self._maps = tuple(maps)
def __init_subclass__(cls) -> None:
raise TypeError(
"Inheritance class {} from ChainMapProxy "
"is forbidden".format(cls.__name__)
)
def __getitem__(self, key: str) -> Any:
for mapping in self._maps:
try:
return mapping[key]
except KeyError:
pass
raise KeyError(key)
def get(self, key: str, default: Any = None) -> Any:
return self[key] if key in self else default
def __len__(self) -> int:
# reuses stored hash values if possible
return len(set().union(*self._maps)) # type: ignore[arg-type]
def __iter__(self) -> Iterator[str]:
d: Dict[str, Any] = {}
for mapping in reversed(self._maps):
# reuses stored hash values if possible
d.update(mapping)
return iter(d)
def __contains__(self, key: object) -> bool:
return any(key in m for m in self._maps)
def __bool__(self) -> bool:
return any(self._maps)
def __repr__(self) -> str:
content = ", ".join(map(repr, self._maps))
return f"ChainMapProxy({content})"
# https://tools.ietf.org/html/rfc7232#section-2.3
_ETAGC = r"[!#-}\x80-\xff]+"
_ETAGC_RE = re.compile(_ETAGC)
_QUOTED_ETAG = rf'(W/)?"({_ETAGC})"'
QUOTED_ETAG_RE = re.compile(_QUOTED_ETAG)
LIST_QUOTED_ETAG_RE = re.compile(rf"({_QUOTED_ETAG})(?:\s*,\s*|$)|(.)")
ETAG_ANY = "*"
@attr.s(auto_attribs=True, frozen=True, slots=True)
class ETag:
value: str
is_weak: bool = False
def validate_etag_value(value: str) -> None:
if value != ETAG_ANY and not _ETAGC_RE.fullmatch(value):
raise ValueError(
f"Value {value!r} is not a valid etag. Maybe it contains '\"'?"
)
def parse_http_date(date_str: Optional[str]) -> Optional[datetime.datetime]:
"""Process a date string, return a datetime object"""
if date_str is not None:
timetuple = parsedate(date_str)
if timetuple is not None:
with suppress(ValueError):
return datetime.datetime(*timetuple[:6], tzinfo=datetime.timezone.utc)
return None
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