def normalize(body_part_tup,):
    """Normalize a tuple of BodyPart objects to a string.

    Normalization is done by sorting the body_parts by the Content- Disposition headers,
    which is typically on the form, ``form-data; name="name_of_part``.

    """
    return '\n\n'.join(
        [
            '{}\n\n{}'.format(
                str(p.headers[b'Content-Disposition'], p.encoding), p.text
            )
            for p in sorted(
                body_part_tup, key=lambda p: p.headers[b'Content-Disposition']
            )
        ]
    )
Normalize a tuple of BodyPart objects to a string.

    Normalization is done by sorting the body_parts by the Content- Disposition headers,
    which is typically on the form, ``form-data; name="name_of_part``.