MIME-Version in interpart, Python MIMEMultipart

[berb.web]

list -

using python's MIMEMultipart() object I've noticed that it interjects
a 'MIME-Version' in the interpart header, like so...

<snip>
--some_MIME_Boundry
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit

some_test
</snip>

Now, RFC1521, section 3 reads:
Note that the MIME-Version header field is required at the top level
of a message. It is not required for each body part of a multipart
entity. It is required for the embedded headers of a body of type
"message" if and only if the embedded message is itself claimed to
be
MIME-conformant.

What I'm wondering is if anyone knows if the inclusion of the MIME-
Version in the interpart header is invalid. It does not look like it
to me, byt I'm looking for your opinions.

Regards,
berb