/**
  * Update a specific schedule for a campaign
  * @param string $accessToken - Constant Contact OAuth2 access token
  * @param int $campaignId - Campaign id to be scheduled
  * @param Schedule $schedule - Schedule to retrieve
  * @return Schedule
  */
 public function updateSchedule($accessToken, $campaignId, Schedule $schedule)
 {
     $baseUrl = Config::get('endpoints.base_url') . sprintf(Config::get('endpoints.campaign_schedule'), $campaignId, $schedule->id);
     $url = $this->buildUrl($baseUrl);
     $response = parent::getRestClient()->put($url, parent::getHeaders($accessToken), $schedule->toJson());
     return Schedule::create(json_decode($response->body, true));
 }