Issue #6488: Explain the XPath support of xml.etree.ElementTree, with code samples and a reference. Also fix the other nits mentioned in the issue.
Issue #6488: Explain the XPath support of xml.etree.ElementTree, with code
samples and a reference. Also fix the other nits mentioned in the issue.

This also partially addresses issue #14006.

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