Calculates the internal energy of the AMPAL object.

        This method is assigned to the buff_internal_energy property,
        using the default arguments.

        Parameters
        ----------
        assign_ff: bool, optional
            If true the force field will be updated if required.
        ff: BuffForceField, optional
            The force field to be used for scoring.
        mol2: bool, optional
            If true, mol2 style labels will also be used.
        force_ff_assign: bool, optional
            If true, the force field will be completely reassigned, ignoring the
            cached parameters.

        Returns
        -------
        BUFF_score: BUFFScore
            A BUFFScore object with information about each of the interactions and
            the atoms involved.

def get_internal_energy(self, assign_ff=True, ff=None, mol2=False,
                            force_ff_assign=False):
        """Calculates the internal energy of the AMPAL object.

        This method is assigned to the buff_internal_energy property,
        using the default arguments.

        Parameters
        ----------
        assign_ff: bool, optional
            If true the force field will be updated if required.
        ff: BuffForceField, optional
            The force field to be used for scoring.
        mol2: bool, optional
            If true, mol2 style labels will also be used.
        force_ff_assign: bool, optional
            If true, the force field will be completely reassigned, ignoring the
            cached parameters.

        Returns
        -------
        BUFF_score: BUFFScore
            A BUFFScore object with information about each of the interactions and
            the atoms involved.
        """
        if not ff:
            ff = global_settings['buff']['force_field']
        if assign_ff:
            self.update_ff(ff, mol2=mol2, force_ff_assign=force_ff_assign)
        interactions = find_intra_ampal(self, ff.distance_cutoff)
        buff_score = score_interactions(interactions, ff)
        return buff_score