(self)
:return: The name of the model field to return when calling ``get_doc_ids``. Return a string
                 or a dict mapping an alias to a SQL expression
:return: The name of the model field to return when calling ``get_doc_ids``. Return a string
                 or a dict mapping an alias to a SQL expression
: return : The name of the model field to return when calling get_doc_ids . Return a string or a dict mapping an alias to a SQL expression
def id_field(self):
        """
        :return: The name of the model field to return when calling ``get_doc_ids``. Return a string
                 or a dict mapping an alias to a SQL expression
        """
        raise NotImplementedError
def id_field ( self ) : raise NotImplementedError