Function to convert an email Message to standard format string

    :param message: email.Message to be converted to standard string
    :return: the standard representation of the email message in bytes

def canonicalize(message):
    """
    Function to convert an email Message to standard format string

    :param message: email.Message to be converted to standard string
    :return: the standard representation of the email message in bytes
    """

    if message.is_multipart() \
            or message.get('Content-Transfer-Encoding') != 'binary':

        return mime_to_bytes(message, 0).replace(
            b'\r\n', b'\n').replace(b'\r', b'\n').replace(b'\n', b'\r\n')
    else:
        message_header = ''
        message_body = message.get_payload(decode=True)
        for k, v in message.items():
            message_header += '{}: {}\r\n'.format(k, v)
        message_header += '\r\n'
        return message_header.encode('utf-8') + message_body