ArgumentCountError: Too few arguments to function Twig\Environment::loadTemplate()

ArgumentCountError: Too few arguments to function Twig\Environment::loadTemplate(), 1 passed in modules/custom/mail_composer/src/Email.php on line 69 and at least 2 expected in Twig\Environment->loadTemplate() (line 330 of /var/www/gbyte/vendor/twig/twig/src/Environment.php).

This error shows up in Drupal 10.x.