docs: def schedule_email(message, to, subject=None, sender=None, priority=None):
      """Schedules an email message for delivery.
  
      :param dict, str message: str or dict: use str for simple text email;
          dict - to compile email from a template (default: `sitemessage/messages/email_html__smtp.html`).
      :param list|str|unicode to: recipients addresses or Django User model heir instances
      :param str subject: email subject
      :param User sender: User model heir instance
      :param int priority: number describing message priority. If set overrides priority provided with message type.
      """
  
      if SHORTCUT_EMAIL_MESSAGE_TYPE:
          message_cls = get_registered_message_type(SHORTCUT_EMAIL_MESSAGE_TYPE)
  
      else:
  
          if isinstance(message, dict):
              message_cls = EmailHtmlMessage
          else:
              message_cls = EmailTextMessage
  
      schedule_messages(
          message_cls(subject, message),
          recipients(SHORTCUT_EMAIL_MESSENGER_TYPE, to),
          sender=sender, priority=priority
      )