function addOptionMethod( PluginClass ) {
				// don't overwrite original option method
				if ( PluginClass.prototype.option ) {
					return;
				}

			  // option setter
			  PluginClass.prototype.option = function( opts ) {
			    // bail out if not an object
			    if ( !$.isPlainObject( opts ) ){
			      return;
			    }
			    this.options = $.extend( true, this.options, opts );
			  };
			}
adds option method -> $().plugin('option', {...})
@param {Function} PluginClass - constructor class