No API reference for DataFrameGroupBy and "combining" step
At least by searching google, I found no references for the DataFrameGroupBy. The docs  at http://pandas.pydata.org/pandas-docs/dev/groupby.html speak about a "GroupBy object"...

What are all the functions of that object? Using IPython, I get inline help, but this informations seems to be missing in the online docs.

I'm also missing the "combine" step in the split-apply-combine doc: how can values be added to the original dataframe? I only found something about transform, which returns a complete dataframe. grouped.apply() returns a single Series. Did I miss something or is the combine step really just a "merge the new dataframe/series with the old one".
