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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 get_trg_ids(self, src_ids: np.ndarray) -> np.ndarray: """ Lookup possible target ids for input sequence of source ids. :param src_ids: Sequence(s) of source ids (any shape). :return: Possible target ids for source (unique sorted, always includes special symbols). """

        # TODO: When MXNet adds support for set operations, we can migrate to avoid conversions to/from NumPy.
        unique_src_ids = np.lib.arraysetops.unique(src_ids)
        trg_ids = np.lib.arraysetops.union1d(self.always_allow, self.lex[unique_src_ids, :].reshape(-1))
        return trg_ids