code: function notDefined(keyToTest, keySupplied, instance) {
    return new RegExp("^" + keyToTest + "$").test(keySupplied.toString()) && !instance.hasOwnProperty(keyToTest);
  }
docs: Simple function to check if a supplied key matches a string of your
  choosing and that string is not a defined property on the instance
  passed to the check.
  
  @method GQLBaseEnv~notDefined
  @memberof GQLBaseEnv
  @since 2.5.0
  
  @param {string} keyToTest a String denoting the property you wish to test
  @param {mixed} keySupplied a value, coerced `toString()`, to compare to
  `keyToTest`
  @param {mixed} instance an object instance to check `hasOwnProperty` on for
  the `keyToTest` supplied.
  @return {Boolean} true if the property matches the supplied key and that
  property is not an ownedProperty of the instance supplied.