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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 broadcast(cast, onto, cast_on=None, onto_on=None, cast_index=False, onto_index=False):
 """ Register a rule for merging two tables by broadcasting one onto the other. Parameters cast, onto : str Names of registered tables. cast_on, onto_on : str, optional Column names used for merge, equivalent of ``left_on``/``right_on`` parameters of pandas.merge. cast_index, onto_index : bool, optional Whether to use table indexes for merge. Equivalent of ``left_index``/``right_index`` parameters of pandas.merge. """

    logger.debug(
        'registering broadcast of table {!r} onto {!r}'.format(cast, onto))
    _BROADCASTS[(cast, onto)] = \
        Broadcast(cast, onto, cast_on, onto_on, cast_index, onto_index)