code: function isEmptyDataObject( obj ) {
  	for ( var name in obj ) {
  
  		// if the public data object is empty, the private is still empty
  		if ( name === "data" && jQuery.isEmptyObject( obj[name] ) ) {
  			continue;
  		}
  		if ( name !== "toJSON" ) {
  			return false;
  		}
  	}
  
  	return true;
  }
docs: checks a cache object for emptiness