code: function result(rule) {
    var r = {}
  
    var reserved = ['filename', 'exists', 'grep', 'jsonKeyExists']
  
    Object.keys(rule).forEach(function(key) {
      if (reserved.indexOf(key) !== -1) return
      r[key] = rule[key]
    })
  
    return r
  }
docs: Return an object created by removing all special properties from a rules object.