Returns the coordination geometry of the given IUCr symbol.
        :param IUCr_symbol: The IUCr symbol of the coordination geometry.

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