def METHOD_NAME(self, frame_size):
    """
    This internal method is called by the connection or stream that owns
    the flow control manager. It handles the generic behaviour of flow
    control managers: namely, keeping track of the window size.
    """
    rc = self.increase_window_size(frame_size)
    self.window_size -= frame_size
    self.window_size += rc
    return rc