code: def _send_mail(subject_or_message: Optional[Union[str, Message]] = None,
                 to: Optional[Union[str, List[str]]] = None,
                 template: Optional[str] = None,
                 **kwargs):
      
      subject_or_message = subject_or_message or kwargs.pop('subject')
      to = to or kwargs.pop('recipients', [])
      msg = make_message(subject_or_message, to, template, **kwargs)
      with mail.connect() as connection:
          connection.send(msg)
docs: The default function used for sending emails.
  
      :param subject_or_message: A subject string, or for backwards compatibility with
                                 stock Flask-Mail, a :class:`~flask_mail.Message` instance
      :param to: An email address, or a list of email addresses
      :param template: Which template to render.
      :param kwargs: Extra kwargs to pass on to :class:`~flask_mail.Message`