code: function Machines (sigTerm) {
    if (!(this instanceof Machines))
      return new Machines(sigTerm);
  
    this._sigTerm = sigTerm;
    this._devices = {};
  
    EventEmitter.call(this);
  }
docs: Describes the conjunction of machines to
  search for.
  
  emits:
  - removeddevice,
  - device,
  - invaliddevice,
  - validdevice.
  
  @param {string} sigTerm signature string to
  match.