def dataReceived(data):
        """
        Called whenever data is received.

        Use this method to translate to a higher-level message.  Usually, some
        callback will be made upon the receipt of each complete protocol
        message.

        Please keep in mind that you will probably need to buffer some data
        as partial (or multiple) protocol messages may be received!  We
        recommend that unit tests for protocols call through to this method
        with differing chunk sizes, down to one byte at a time.

        @param data: bytes of indeterminate length
        @type data: L{bytes}
        """

        Called whenever data is received.

        Use this method to translate to a higher-level message.  Usually, some
        callback will be made upon the receipt of each complete protocol
        message.

        Please keep in mind that you will probably need to buffer some data
        as partial (or multiple) protocol messages may be received!  We
        recommend that unit tests for protocols call through to this method
        with differing chunk sizes, down to one byte at a time.

        @param data: bytes of indeterminate length
        @type data: L{bytes}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/interfaces.py