Nit: instead of having doctests here, it would be better to put a test in `pyspark/tests.py` for this particular case. The reason is that doctests should ideally be self-contained and should also serve as documentation, but these depend on some files that the reader of the docs won't know about.

Instead, maybe add `@param` statements for the arguments. Look at `pyspark/conf.py` to see how to format these in Epydoc.