code: public function getEntityAlias($entity)
      {
          if (!($this->doctrine instanceof Registry)) {
              return null;
          }
  
          $class = get_class($entity);
  
          $namespaces = $this
              ->doctrine
              ->getManager()
              ->getConfiguration()
              ->getEntityNamespaces();
  
          foreach ($namespaces as $ns_alias => $ns) {
              if (strpos($class, $ns) === 0) {
                  return $ns_alias.':'.ltrim(str_replace($ns, '', $class), '\\');
              }
          }
  
          return null;
      }
docs: @param object $entity
  
  @return string|null