def __init__(self, extData={}):
        """
        @param extData: a dict of extended_name : extended_data items
        to be sent to the server.
        """
        FileTransferBase.__init__(self)
        self.extData = {}
        self.counter = 0
        self.openRequests = {} # id -> Deferred

        @param extData: a dict of extended_name : extended_data items
        to be sent to the server.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/ssh/filetransfer.py