rem: return this.select(function(value) { return value != null; 
add: return this.map(function(value, index) { return iterator(collections.pluck(index)); 
context:     return this.select(function(value) {      return value != null;    });
meta: 7608	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/7608/d556a0875c83645645bd2067594241546d26d052/prototype.js/buggy/web/js/prototype.js