step = function (frame) {
      var dependencies, i, len;
      dependencies = (type == 'frame') ? [frame] : (frame[type + 's'] || []);

      for (i = 0, len = dependencies.length; i < len; i++) {
        callback.call(controller, dependencies[i]);
      }

      return frame;
    }
An invalid InteractionBox object.

You can use this InteractionBox instance in comparisons testing
whether a given InteractionBox instance is valid or invalid. (You can also use the
InteractionBox.valid property.)

@static
@type {Leap.InteractionBox}
@name Invalid
@memberof Leap.InteractionBox