code: function isURLSearchParams(obj) {
  	// Duck-typing as a necessary condition.
  	if (typeof obj !== 'object' ||
  		typeof obj.append !== 'function' ||
  		typeof obj.delete !== 'function' ||
  		typeof obj.get !== 'function' ||
  		typeof obj.getAll !== 'function' ||
  		typeof obj.has !== 'function' ||
  		typeof obj.set !== 'function') {
  		return false;
  	}
  
  	// Brand-checking and more duck-typing as optional condition.
  	return obj.constructor.name === 'URLSearchParams' ||
  		Object.prototype.toString.call(obj) === '[object URLSearchParams]' ||
  		typeof obj.sort === 'function';
  }
docs: Detect a URLSearchParams object
  ref: https://github.com/bitinn/node-fetch/issues/296#issuecomment-307598143
  
  @param   Object  obj     Object to detect by type or brand
  @return  String