code: def _proc_sym_top(self):
          
          if abs(self.eigvals[0] - self.eigvals[1]) < self.eig_tol:
              ind = 2
          elif abs(self.eigvals[1] - self.eigvals[2]) < self.eig_tol:
              ind = 0
          else:
              ind = 1
          logger.debug("Eigenvalues = %s." % self.eigvals)
          unique_axis = self.principal_axes[ind]
          self._check_rot_sym(unique_axis)
          logger.debug("Rotation symmetries = %s" % self.rot_sym)
          if len(self.rot_sym) > 0:
              self._check_perpendicular_r2_axis(unique_axis)
  
          if len(self.rot_sym) >= 2:
              self._proc_dihedral()
          elif len(self.rot_sym) == 1:
              self._proc_cyclic()
          else:
              self._proc_no_rot_sym()
docs: Handles symetric top molecules which has one unique eigenvalue whose
          corresponding principal axis is a unique rotational axis.  More complex
          handling required to look for R2 axes perpendicular to this unique
          axis.