def _slice_datetime_repr_prefix(obj_repr):
    """Takes a default "datetime", "date", or "timedelta" repr and
    returns it with the module prefix sliced-off::

        >>> _slice_datetime_repr_prefix('datetime.date(2020, 12, 25)')
        'date(2020, 12, 25)'
    """
    # The following implementation (using "startswith" and "[9:]")
    # may look clumsy but it can run up to 10 times faster than a
    # more concise "re.compile()" and "regex.sub()" approach. In
    # some situations, this function can get called many, many
    # times. DON'T GET CLEVER--KEEP THIS FUNCTION FAST.
    if obj_repr.startswith('datetime.datetime(') \
            or obj_repr.startswith('datetime.date(') \
            or obj_repr.startswith('datetime.timedelta('):
        return obj_repr[9:]
    return obj_repr