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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 from_timestamp( timestamp, tz=UTC # type: Union[int, float] # type: Union[str, _Timezone] """ Create a DateTime instance from a timestamp. """

    dt = _datetime.datetime.utcfromtimestamp(timestamp)

    dt = datetime(
        dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second, dt.microsecond
    )

    if tz is not UTC or tz != "UTC":
        dt = dt.in_timezone(tz)

    return dt