code: func (i *Intervals) Merge(m *Intervals) {
  	m.mu.RLock()
  	defer m.mu.RUnlock()
  	i.mu.Lock()
  	defer i.mu.Unlock()
  
  	for _, r := range m.ranges {
  		i.add(r[0], r[1])
  	}
  }
docs: // Merge adds all the intervals from the m Interval to current one.