Not clear why this accessor (XMLElementList) is designed differently with others.
In other accessors, we use parent_xpath and tag_name to locate a element, by element_by_parent().
But this accessor use find(parent_xpath) and parent.getchildren() to get the children.
It seems elements in list are the brothers of tag_name but not the children of tag_name.

Wish your explanation and more comment here.
Thanx.