docs: function instanceOfInterface(instance, target) {
          var x,
              interfaces = instance.$static[$class].interfaces;
  
          for (x = interfaces.length - 1; x >= 0; x -= 1) {
              if (interfaces[x] === target || interfaceDescendantOf(interfaces[x], target)) {
                  return true;
              }
          }
  
          return false;
      }