def fetch(messages, uid):
        """
        Retrieve one or more messages.

        @type messages: C{MessageSet}
        @param messages: The identifiers of messages to retrieve information
            about

        @type uid: L{bool}
        @param uid: If true, the IDs specified in the query are UIDs; otherwise
            they are message sequence IDs.

        @rtype: Any iterable of two-tuples of message sequence numbers and
            implementors of C{IMessageIMAP}.
        """

        Retrieve one or more messages.

        @type messages: C{MessageSet}
        @param messages: The identifiers of messages to retrieve information
            about

        @type uid: L{bool}
        @param uid: If true, the IDs specified in the query are UIDs; otherwise
            they are message sequence IDs.

        @rtype: Any iterable of two-tuples of message sequence numbers and
            implementors of C{IMessageIMAP}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/interfaces.py