code: def set_irreps(self,
                     q,
                     is_little_cogroup=False,
                     nac_q_direction=None,
                     degeneracy_tolerance=1e-4):
          
  
          if self._dynamical_matrix is None:
              msg = ("Dynamical matrix has not yet built.")
              raise RuntimeError(msg)
  
          self._irreps = IrReps(
              self._dynamical_matrix,
              q,
              is_little_cogroup=is_little_cogroup,
              nac_q_direction=nac_q_direction,
              factor=self._factor,
              symprec=self._symprec,
              degeneracy_tolerance=degeneracy_tolerance,
              log_level=self._log_level)
  
          return self._irreps.run()
docs: Identify ir-reps of phonon modes.
  
          The design of this API is not very satisfactory and is expceted
          to be redesined in the next major versions once the use case
          of the API for ir-reps feature becomes clearer.