'Set the :class:`WidgetsScheme` instance to manage.'

def set_scheme(self, scheme):

    self.__scheme = scheme
    self.__signal_manager = scheme.findChild(SignalManager)
    self.__signal_manager.processingStarted[SchemeNode].connect(self.__on_processing_started)
    self.__signal_manager.processingFinished[SchemeNode].connect(self.__on_processing_finished)
    scheme.node_added.connect(self.add_widget_for_node)
    scheme.node_removed.connect(self.remove_widget_for_node)
    scheme.runtime_env_changed.connect(self.__on_env_changed)
    scheme.installEventFilter(self)
