Restful API in Python- Getting an HTTP error for a POST function

I am having success using the Restful API in retrieving data from Eloqua (using the library created by Fred Sakr ) but when I try the POST function I keep getting an error.

Here is the code:

Here is the error:

I am puzzled because the data I am passing in the live docs works, but it does not work with the Python code.

If anyone has any ideas on how to make the Python code work, it would be greatly appreciated. Thanks!