Shortcut for getting examples of the first few groups from a GroupBy?
For visualization/testing purposes, I'm often interested in looking at the first example group(s) from a groupby operation.

Is there a convenient shortcut for this? The best I could come up with is `pd.concat([x for _, x in itertools.islice(group, 3)])` which seemed awkward to me.

Note that this is a _different_ use-case from `.first()`/`.head()`, which returns the first example from each group -- here I want full examples of the first few groups.
