code: function(sessionToken) {
          return this._fetchUserBySessionToken(sessionToken).then(user =>
            user._handleSaveResult(true).then(() => user)
          );
        }
docs: Logs in a user with a session token. On success, this saves the session
  to disk, so you can retrieve the currently logged in user using
  <code>current</code>.
  
  @param {String} sessionToken The sessionToken to log in with.
  @return {Promise} A promise that is fulfilled with the user when
  the login completes.