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main.py

from typing_extensions import TypeIs
from typing import Any, Awaitable, TypeVar, Union
T = TypeVar('T')
def is_awaitable(val: object) -> TypeIs[Awaitable[Any]]: pass
def main(a: Union[Awaitable[T], T]) -> None:
    if is_awaitable(a):
        reveal_type(a)  # N: Revealed type is "Union[typing.Awaitable[T`-1], typing.Awaitable[Any]]"
    else:
        reveal_type(a)  # N: Revealed type is "T`-1"