def do_set_row_col_sizes(self, sizes):
raise NotImplementedError<EOL>
Copy child size information into the underlying grid data structure.

The `sizes` argument is a dictionary mapping 1-dimensional child 
indices to the sizes provided by `add()` (e.g. 0, 'expand', etc).  This 
information either needs to be applied to the columns (`HBox`) or rows 
(`VBox`) of the underlying grid data structure.