code: def disconnect(self, callback):
          
          try:
              self._callbacks.remove(callback)
          except ValueError:
              self._callbacks.remove(ref(callback))
docs: Disconnects a callback from this signal.
  
          :param callback: The callback to disconnect.
          :param weak: A flag that must have the same value than the one
              specified during the call to `connect`.
  
          .. warning::
              If the callback is not connected at the time of call, a
              :class:`ValueError` exception is thrown.
  
          .. note::
              You may call `disconnect` from a connected callback.