nl_tokens: gets the model in the stack at the index negative values start at root
pl_tokens: function ( index ) { if ( ! _ . isNumber ( index ) || isNaN ( index ) ) index = 0 ; if ( index < 0 ) return this . getAllModels ( ) [ ~ index ] ; var model = this ; while ( index && model ) { model = model . <mask> ; index -- ; } return model ; }