docs: function Mixin(hostObject, proxyMethods) { // , other args - passed to init method
      check(hostObject, Match.Optional(Match.OneOf(Object, Function)));
  
      // store hostObject
      Object.defineProperty(this, '_hostObject', { value: hostObject });
  
      // proxy methods to hostObject
      if (proxyMethods)
          this._createProxyMethods(proxyMethods);
  
      // calling init if it is defined in the class
      if (this.init)
          this.init.apply(this, arguments);
  }