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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 _to_M8(key, tz=None):
 """ Timestamp-like => dt64 """

    if not isinstance(key, Timestamp):
        # this also converts strings
        key = Timestamp(key)
        if key.tzinfo is not None and tz is not None:
            # Don't tz_localize(None) if key is already tz-aware
            key = key.tz_convert(tz)
        else:
            key = key.tz_localize(tz)

    return np.int64(conversion.pydt_to_i8(key)).view(_NS_DTYPE)