Create a Mail object from an instance of
        email.message.EmailMessage.

        :type message: email.message.EmailMessage
        :rtype: Mail

def from_EmailMessage(cls, message):
        """Create a Mail object from an instance of
        email.message.EmailMessage.

        :type message: email.message.EmailMessage
        :rtype: Mail
        """
        mail = cls(
            from_email=Email(message.get('From')),
            subject=message.get('Subject'),
            to_emails=Email(message.get('To')),
        )
        try:
            body = message.get_content()
        except AttributeError:
            # Python2
            body = message.get_payload()
        mail.add_content(Content(
            message.get_content_type(),
            body.strip()
        ))
        for k, v in message.items():
            mail.add_header(Header(k, v))
        return mail