code: func (sg *SampleGroup) MinRate() int64 {
  	m := int64(0)
  	for i, s := range sg.Samples {
  		if i == 0 {
  			m = s.Rate()
  		}
  		m = min(m, s.Rate())
  	}
  	return m
  }
docs: // MinRate returns the smallest message rate in the SampleGroup