code: function(mobilePhone, password) {
          var user = AV.Object._create('_User');
          user._finishFetch({
            mobilePhoneNumber: mobilePhone,
            password: password,
          });
          return user.logIn();
        }
docs: Logs in a user with a mobile phone number and password. On success, this
  saves the session to disk, so you can retrieve the currently logged in
  user using <code>current</code>.
  
  @param {String} mobilePhone The user's mobilePhoneNumber
  @param {String} password The password to log in with.
  @return {Promise} A promise that is fulfilled with the user when
  the login completes.
  @see AV.User#logIn