I am using the email module and creating a message object out of both ASCII and Unicode files that are essentially emails. 
The emails include a secretary responding in one portion and in others the boss creating the email. These emails were extracted from pst files (i.e. from outlook or something similar). If you are familiar with company emails then you'll know what I'm talking about. 
Also if do have multiparts and I use get_payload() on those parts and specify an index, i, how are the indices arranged? As in what is in the indices? Are they the parts of an email?
A multipart message is basically a nested e-mail message. The embedded messages are ordered in the order that the messages were attached to the containing e-mail. There isn't and index embedded in the e-mail (if I understand your question correctly) - get_payload() would return a list of the embedded e-mail messages.
If you saw the raw e-mail and how the MIME parts are arranged it would clarify your understanding.
What exactly is a python sub message object if is_multipart is true and how does python organize them?