'Retrieves a set of Match objects that have the given tag defined.
:param tag:
:type tag: str
:param predicate:
:type predicate:
:param index:
:type index: int
:return: set of matches
:rtype: set[Match]'

def tagged(self, tag, predicate=None, index=None):

    return filter_index(_BaseMatches._base(self._tag_dict[tag]), predicate, index)
