REF: de-duplicate symmetric_difference, _union
Also fixes buglet in CategoricalIndex.equals(MultiIndex)
can you rebase once more rebase yeah seeing failures on master rebased + green wow nice This seems to have caused several performance regressions, see https://pandas.pydata.org/speed/pandas/#regressions?sort=1&dir=desc (the ones for commit "bf72b70b") Opened https://github.com/pandas-dev/pandas/issues/42239 to track this regression