text: 'use strict'
  
  var difference = require('array-differ')
  var extend = require('xtend')
  
  module.exports = function keyDifference (obj) {
    var others = [].slice.call(arguments, 1)
    var source = Object.keys(obj)
    var rest = Object.keys(extend.apply(null, others))
    return difference(source, rest)
  }
  