def destroy(self):
        """ Destroys the clipboard by relieving all model references.
        """
        self.destroy_all_models_in_dict(self.model_copies)
        self.model_copies = None
        self.copy_parent_state_id = None
        self.outcome_id_mapping_dict = None
        self.port_id_mapping_dict = None
        self.state_id_mapping_dict = None
Destroys the clipboard by relieving all model references.