code: func (j *Job) RequiredTarget() (string, bool) {
  	requirements := j.requirements()
  
  	var machIDs []string
  	var ok bool
  	// Best case: look for modern declaration
  	machIDs, ok = requirements[fleetMachineID]
  	if ok && len(machIDs) != 0 {
  		return machIDs[0], true
  	}
  
  	// First fall back to the deprecated syntax
  	machIDs, ok = requirements[deprecatedXConditionPrefix+fleetMachineID]
  	if ok && len(machIDs) != 0 {
  		return machIDs[0], true
  	}
  
  	// Finally, fall back to the legacy option if it exists. This is
  	// unlikely to actually work as the user intends, but it's better to
  	// prevent a job from starting that has a legacy requirement than to
  	// ignore the requirement and let it start.
  	bootIDs, ok := requirements[deprecatedXConditionPrefix+fleetMachineBootID]
  	if ok && len(bootIDs) != 0 {
  		return bootIDs[0], true
  	}
  
  	return "", false
  }
docs: // RequiredTarget determines whether or not this Job must be scheduled to
  // a specific machine. If such a requirement exists, the first value returned
  // represents the ID of such a machine, while the second value will be a bool
  // true. If no requirement exists, an empty string along with a bool false
  // will be returned.