code: def get_geometries(self, coordination=None, returned='cg'):
          
          geom = list()
          if coordination is None:
              for gg in self.cg_list:
                  if returned == 'cg':
                      geom.append(gg)
                  elif returned == 'mp_symbol':
                      geom.append(gg.mp_symbol)
          else:
              for gg in self.cg_list:
                  if gg.get_coordination_number() == coordination:
                      if returned == 'cg':
                          geom.append(gg)
                      elif returned == 'mp_symbol':
                          geom.append(gg.mp_symbol)
          return geom
docs: Returns a list of coordination geometries with the given coordination number.
          :param coordination: The coordination number of which the list of coordination geometries are returned.