code: def context_notify_cb(self, context, _):
          
          state = pa_context_get_state(context)
  
          if state == PA_CONTEXT_READY:
              pa_operation_unref(
                  pa_context_get_server_info(context, self._server_info_cb, None))
  
              pa_context_set_subscribe_callback(context, self._update_cb, None)
  
              pa_operation_unref(pa_context_subscribe(
                  context, PA_SUBSCRIPTION_EVENT_CHANGE | PA_SUBSCRIPTION_MASK_SINK | PA_SUBSCRIPTION_MASK_SERVER, self._success_cb, None))
docs: 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)