problème de module personnalisé "send_email"

Bonjour
Je suis débutant et j'ai un problème avec ce module qui envoie une notification lorsque la création d'une nouveaux type de contenue bulletin de soin ou bulletin d'incapacité !

<?php

use Drupal\Component\Utility\SafeMarkup;
use Drupal\Core\Entity\EntityInterface;

/**
* Implements hook_mail().
* @param $key
* @param $message
* @param $params
*/
function send_email_mail($key, & $message, $params)
{
$options = array(
'langcode' => $message['langcode'],
);
switch ($key) {
case 'send_email':
$message['from'] = \Drupal::config('system.site')->get('mail');
$message['subject'] = t('Node created: @title', array('@title' => $params['node_title']), $options);
break;
}
}
/**
* Implements hook_entity_insert().
* @param EntityInterface $entity
*/
function send_email_entity_insert(Drupal\Core\Entity\EntityInterface $entity)
{
if (($entity->getEntityTypeId() === 'node' && $entity->bundle() == 'disability_bulletin') || ($entity->getEntityTypeId() === 'node' && $entity->bundle() == 'care_bulletin')) {
$mailManager = \Drupal::service('plugin.manager.mail');
$module = 'send_email';
$key = 'node_insert';
$to = \Drupal::currentUser()->getEmail();
$params['node_title'] = $entity->label();
$langcode = \Drupal::currentUser()->getPreferredLangcode();
$send = true;
$result = $mailManager->mail($module, $key, $to, $langcode, $params,NULL, $send);
if ($result['result'] == true) {
$message = t('There was a problem sending your email notification to @email for creating node @id.', array('@email' => $to, '@id' => $entity->id()));
\Drupal::logger('send_email')->error($message);
return;
}
$message = t('An email notification has been sent to @email for creating node @id.', array('@email' => $to, '@id' => $entity->id()));
drupal_set_message($message);
\Drupal::logger('send_email')->notice($message);
}
}