Calculates the energy of the reaction.

        Args:
            energies ({Composition: float}): Energy for each composition.
                E.g ., {comp1: energy1, comp2: energy2}.

        Returns:
            reaction energy as a float.

def calculate_energy(self, energies):
        """
        Calculates the energy of the reaction.

        Args:
            energies ({Composition: float}): Energy for each composition.
                E.g ., {comp1: energy1, comp2: energy2}.

        Returns:
            reaction energy as a float.
        """
        return sum([amt * energies[c] for amt, c in zip(self._coeffs,
                                                        self._all_comp)])