def writeChunk(offset, data):
        """
        Write to the file.

        This method returns when the write completes, or a Deferred that is
        called when it completes.

        @param offset: an integer that is the index to start from in the file.
        @param data: a string that is the data to write.
        """

        Write to the file.

        This method returns when the write completes, or a Deferred that is
        called when it completes.

        @param offset: an integer that is the index to start from in the file.
        @param data: a string that is the data to write.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/interfaces.py