Checks if the lambda function name format contains only known elements
        :return: True on success, ValueError raised on error

def _validate_lambda_funcname_format(self):
        '''
        Checks if the lambda function name format contains only known elements
        :return: True on success, ValueError raised on error
        '''
        try:
            if self._lambda_funcname_format:
                known_kwargs = dict(stage='',
                                    api='',
                                    resource='',
                                    method='')
                self._lambda_funcname_format.format(**known_kwargs)
            return True
        except Exception:
            raise ValueError('Invalid lambda_funcname_format {0}.  Please review '
                             'documentation for known substitutable keys'.format(self._lambda_funcname_format))