code: def disconnect(self, callback=None):
          
          if callback is None:
              self._callbacks = []
              self._callback_refs = []
          else:
              callback = self._normalize_cb(callback)
              if callback in self._callbacks:
                  idx = self._callbacks.index(callback)
                  self._callbacks.pop(idx)
                  self._callback_refs.pop(idx)
docs: Disconnect a callback from this emitter.
  
          If no callback is specified, then *all* callbacks are removed.
          If the callback was not already connected, then the call does nothing.