code: def get_geometry_from_IUPAC_symbol(self, IUPAC_symbol):
          
          for gg in self.cg_list:
              if gg.IUPAC_symbol == IUPAC_symbol:
                  return gg
          raise LookupError(
              'No coordination geometry found with IUPAC symbol "{symbol}"'.format(
                  symbol=IUPAC_symbol))
docs: Returns the coordination geometry of the given IUPAC symbol.
          :param IUPAC_symbol: The IUPAC symbol of the coordination geometry.