How can I make “Leave a comment” translation ready?

I can’t get this line of code translation ready.

<?php 
  comment_form(array ('title_reply' => 'Leave a comment')); 
?>

Thank you very much! Best wishes,
Pierre

Should be put to the translation function.

<?php comment_form(array ('title_reply' => __('Leave a comment', 'mytextdomain'))); ?>

Or use WordPress translation:

<?php comment_form(array ('title_reply' => __('Leave a comment'))); ?>