Issue #12213: make it clear that BufferedRWPair shouldn't be called with the same object as reader and writer, and deemphasize it in document order.
Issue #12213: make it clear that BufferedRWPair shouldn't be called with the
same object as reader and writer, and deemphasize it in document order.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator