code: function() {
            if ( list ) {
              // First, we save the current length
              var start = list.length;
              (function add( args ) {
                _each( args, function( arg ) {
                  var type = _type( arg );
                  if ( type === "function" && ( !options.unique || !self.has( arg ) ) ) {
                    list.push( arg );
                  } else if ( arg && arg.length && type !== "string" ) {
                    // Inspect recursively
                    add( arg );
                  }
                });
              })( arguments );
              // Do we need to add the callbacks to the
              // current firing batch?
              if ( firing ) {
                firingLength = list.length;
              // With memory, if we're not firing then
              // we should call right away
              } else if ( memory ) {
                firingStart = start;
                fire( memory );
              }
            }
            return this;
          }
docs: Add a callback or a collection of callbacks to the list