The :class:`xml.etree.ElementTree.Element` methods
:meth:`~xml.etree.ElementTree.Element.findall`,
:meth:`~xml.etree.ElementTree.Element.iterfind` and
:meth:`~xml.etree.ElementTree.Element.find` avoid quadratic behavior when
using XPath index predicates (``[1]``, ``[last()]``, ``[last()-N]``) on XML
documents with many same-tag siblings.
