code: func (d CPUDetails) KeepOnly(cpus cpuset.CPUSet) CPUDetails {
  	result := CPUDetails{}
  	for cpu, info := range d {
  		if cpus.Contains(cpu) {
  			result[cpu] = info
  		}
  	}
  	return result
  }
docs: // KeepOnly returns a new CPUDetails object with only the supplied cpus.