code: func NewMessageSentSizeStatsHandler(sub Subsystem, vec *prometheus.HistogramVec) *MessageSentSizeStatsHandler {
  	return &MessageSentSizeStatsHandler{
  		baseStatsHandler: baseStatsHandler{
  			subsystem: sub,
  			collector: vec,
  		},
  		vec: vec,
  	}
  }
docs: // NewMessageSentSizeStatsHandler ...