code: func (m *NormMap) add(l int64) bool {
  	assert(m.size <= 256) // once we add > 256 values, we nullify the map in addNumericField and don't use this strategy
  	if l >= math.MinInt8 && l <= math.MaxInt8 {
  		index := int(l + 128)
  		if previous := m.singleByteRange[index]; previous < 0 {
  			m.singleByteRange[index] = int16(m.size)
  			m.size++
  			return true
  		}
  		return false
  	}
  	if _, ok := m.other[l]; !ok {
  		m.other[l] = int16(m.size)
  		m.size++
  		return true
  	}
  	return false
  }
docs: /* Adds an item to the mapping. Returns true if actually added. */