def cbOpened(file):
            """
            File was open for reading. Launch the data transfer channel via
            the file consumer.
            """
            d = file.receive()
            d.addCallback(cbConsumer)
            d.addCallback(lambda ignored: file.close())
            d.addCallbacks(cbSent, ebSent)
            return d

            File was open for reading. Launch the data transfer channel via
            the file consumer.
            
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/ftp.py