code: def __builder_connect_pending_signals(self):
          
          class _MultiHandlersProxy (object):
              def __init__(self, funcs): self.funcs = funcs
              def __call__(self, *args, **kwargs):
                  # according to gtk documentation, the return value of
                  # a signal is the return value of the last executed
                  # handler
                  for func in self.funcs:
                      res = func(*args, **kwargs)
                  return res
  
          final_dict = {n: (v.pop() if len(v) == 1
                            else _MultiHandlersProxy(v))
                        for n, v in self.builder_pending_callbacks.items()}
  
          self._builder.connect_signals(final_dict)
  
          self.builder_connected = True
          self.builder_pending_callbacks = {}
docs: Called internally to actually make the internal Gtk.Builder
          instance connect all signals found in controllers controlling
          self.