def anonymized_formula(self):
        """
        An anonymized formula. Appends charge to the end
        of anonymized composition
        """
        anon_formula = super().anonymized_formula
        chg = self._charge
        chg_str = ""
        if chg > 0:
            chg_str += ("{}{}".format('+', str(int(chg))))
        elif chg < 0:
            chg_str += ("{}{}".format('-', str(int(np.abs(chg)))))
        return anon_formula + chg_str
An anonymized formula. Appends charge to the end
        of anonymized composition