The Python API does not support content_keywords
download in its present form. However,
you can modify http request in the downloader.py to include additional parameters to meet your needs. This way you can fetch content_keywords
as well.
Furthermore, there is a PHP API that supports extracting content_keywords data, which you can search in Google. link
Moreover, there is an extension of the current Python API that extracts data based on custom date ranges automatically for all registered web sites. Find out more about it.