def typed_dict_keys(td):
if isinstance(td, _TypedDictMeta):<EOL><INDENT>return td.__annotations__.copy()<EOL><DEDENT>return None<EOL>
If td is a TypedDict class, return a dictionary mapping the typed keys to types.
    Otherwise, return None. Examples::

        class TD(TypedDict):
            x: int
            y: int
        class Other(dict):
            x: int
            y: int

        typed_dict_keys(TD) == {'x': int, 'y': int}
        typed_dict_keys(dict) == None
        typed_dict_keys(Other) == None