public function create(array $contact, array $options = array())
  {
    $attributes = array_intersect_key($contact, array_flip(self::$keysToPersist));
    if (isset($attributes['custom_fields']) && empty($attributes['custom_fields'])) unset($attributes['custom_fields']);

    list($code, $createdContact) = $this->httpClient->post("/contacts", $attributes, $options);
    return $createdContact;
  }