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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 union(*sets, **kwargs):
 """all unique items which occur in any one of the sets Parameters sets : tuple of indexable objects Returns ------- union of all items in all sets """

    sets = _set_preprocess(sets, **kwargs)
    return as_index( _set_concatenate(sets), axis=0, base=True).unique