code: func (m *metricUnit) Space(s SpaceUnit, dimension int8) MetricUnit {
  	if dimension < -8 || dimension > 7 {
  		panic("dimension has to be between -8 and 7 inclusive")
  	}
  
  	m.repr |= uint32(s)
  	m.repr |= (uint32(dimension) & 0xF) << 28
  	return m
  }
docs: // https://docs.rs/hornet/0.1.0/src/hornet/client/metric/mod.rs.html#375