def sigusr1_handler(self, unused_signum, unused_frame):
        """
        Handle SIGUSR1 signal. Call function which is defined in the
        **settings.SIGUSR1_HANDLER**.
        """
        if self._sigusr1_handler_func is not None:
            self._sigusr1_handler_func(self.context)
Handle SIGUSR1 signal. Call function which is defined in the
        **settings.SIGUSR1_HANDLER**.