def __update_molar_mass(self, compound='<STR_LIT>', element='<STR_LIT>'):
_molar_mass_element = <NUM_LIT:0><EOL>list_ratio = self.stack[compound][element]['<STR_LIT>']['<STR_LIT>']<EOL>list_mass = self.stack[compound][element]['<STR_LIT>']['<STR_LIT>']['<STR_LIT:value>']<EOL>ratio_mass = zip(list_ratio, list_mass)<EOL>for _ratio, _mass in ratio_mass:<EOL><INDENT>_molar_mass_element += np.float(_ratio) * np.float(_mass)<EOL><DEDENT>self.stack[compound][element]['<STR_LIT>']['<STR_LIT:value>'] = _molar_mass_element<EOL>
Re-calculate the molar mass of the element given due to stoichiometric changes

        Parameters:
        ==========
        compound: string (default is '') name of compound
        element: string (default is '') name of element