[Python SDK] Add method to query the raw contents of a message
[Python SDK] Add method to query the raw contents of a message

Summary: Finally it's here, after a lot of head-scratching! Nothing much to say about this diff apart that the metaprogramming parts of the original code really need to be refactored out.

Test Plan: Tested manually.

Reviewers: jennie, spang, emfree

Reviewed By: emfree

Projects: #python-sdk

Differential Revision: https://review.inboxapp.com/D1053

nylas/nylas-python