function IsWritableStreamDefaultController(x) {
		        if (!typeIsObject(x)) {
		            return false;
		        }
		        if (!Object.prototype.hasOwnProperty.call(x, '_controlledWritableStream')) {
		            return false;
		        }
		        return x instanceof WritableStreamDefaultController;
		    }
Request class

Ref: https://fetch.spec.whatwg.org/#request-class

@param   Mixed   input  Url or Request instance
@param   Object  init   Custom options
@return  Void