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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 merge(left, right, how='inner', key=None, left_key=None, right_key=None, left_as='left', right_as='right'):
 """ Performs a join using the union join function. """

    return join(left, right, how, key, left_key, right_key,
                join_fn=make_union_join(left_as, right_as))