code: def get_trg_ids(self, src_ids: np.ndarray) -> np.ndarray:
          
          # 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
docs: 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).