Subclasses should call this method instead of `module.migrate` directly,
        to support `db_config` optional argument.

def _call_migrate(self, module, connection_param):
        """Subclasses should call this method instead of `module.migrate` directly,
        to support `db_config` optional argument.
        """
        args = [connection_param]
        spec = inspect.getargspec(module.migrate)
        if len(spec.args) == 2:
            args.append(self.db_config)
        return module.migrate(*args)