Computes total number of atoms in a reaction formula for elements
        not in external reservoir. This method is used in the calculation
        of reaction energy per mol of reaction formula.

        Args:
            rxt (Reaction): a reaction.

        Returns:
            Total number of atoms for non_reservoir elements.

def _get_elmt_amt_in_rxt(self, rxt):
        """
        Computes total number of atoms in a reaction formula for elements
        not in external reservoir. This method is used in the calculation
        of reaction energy per mol of reaction formula.

        Args:
            rxt (Reaction): a reaction.

        Returns:
            Total number of atoms for non_reservoir elements.
        """
        return sum([rxt.get_el_amount(e) for e in self.pd.elements])