def context_notify_cb(self, context, _):
state = pa_context_get_state(context)<EOL>if state == PA_CONTEXT_READY:<EOL><INDENT>pa_operation_unref(<EOL>pa_context_get_server_info(context, self._server_info_cb, None))<EOL>pa_context_set_subscribe_callback(context, self._update_cb, None)<EOL>pa_operation_unref(pa_context_subscribe(<EOL>context, PA_SUBSCRIPTION_EVENT_CHANGE | PA_SUBSCRIPTION_MASK_SINK | PA_SUBSCRIPTION_MASK_SERVER, self._success_cb, None))<EOL><DEDENT>
Checks wether the context is ready

        -Queries server information (server_info_cb is called)
        -Subscribes to property changes on all sinks (update_cb is called)