Generator for name indices and data subsets for each facet.

(i, j, k), data_ijktuple of ints, DataFrame

The ints provide an index into the {row, col, hue}_names attribute, and the dataframe contains a subset of the full data corresponding to each facet. The generator yields subsets that correspond with the self.axes.flat iterator, or self.axes[i, j] when col_wrap is None.