return module name.

def getTypesModuleName(self):
        '''return module name.
        '''
        assert self.wsdl is not None, 'initialize, call fromWSDL'
        if self.types_module_name is not None:
            return self.types_module_name

        wsm = WriteServiceModule(self.wsdl)
        return wsm.getTypesModuleName()