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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def isinstance_(x, A_tuple):
 """ native isinstance_ with the test for typing.Union overridden """

    if is_union(A_tuple):
        return any(isinstance_(x, t) for t in A_tuple.__args__)
    elif getattr(A_tuple, '__origin__', None) is not None:
        return isinstance(x, A_tuple.__origin__)
    else:
        return isinstance(x, A_tuple)