MAINT improve coverage: openml.datasets.functions

Author: mfeurer

openml/config.py

@@ -51,7 +51,7 @@ def _setup():
     set_cache_directory(cache_dir, private_dir)
 
 
-def set_cache_directory(cachedir, privatedir):
+def set_cache_directory(cachedir, privatedir=None):
     """Set module-wide cache directory.
 
     Sets the cache directory into which to download datasets, tasks etc.