code: def _proc_no_rot_sym(self):
          
          self.sch_symbol = "C1"
          if self.is_valid_op(PointGroupAnalyzer.inversion_op):
              self.sch_symbol = "Ci"
              self.symmops.append(PointGroupAnalyzer.inversion_op)
          else:
              for v in self.principal_axes:
                  mirror_type = self._find_mirror(v)
                  if not mirror_type == "":
                      self.sch_symbol = "Cs"
                      break
docs: Handles molecules with no rotational symmetry. Only possible point
          groups are C1, Cs and Ci.