UP035 recommends change that changes runtime behavior for is_typeddict

[SebbyLaw]

Description

is_typeddict from the typing module does not correctly identify TypedDict from the typing_extensions module:

from typing_extensions import is_typeddict as is_typeddict_te, TypedDict as TypedDict_te
from typing import is_typeddict, TypedDict

class Ext(TypedDict_te):
    a: int

class Reg(TypedDict):
    a: int

print("is_typeddict(Ext):", is_typeddict(Ext))  # False
print("is_typeddict(Reg):", is_typeddict(Reg))  # True
print("is_typeddict_te(Ext):", is_typeddict_te(Ext))  # True
print("is_typeddict_te(Reg):", is_typeddict_te(Reg))  # True

In the description of UP035:

Note that, in some cases, it may be preferable to continue importing members from typing_extensions even after they're added to the Python standard library, as typing_extensions can backport bugfixes and optimizations from later Python versions. This rule thus avoids flagging imports from typing_extensions in such cases.