Find and return clones of all fragments within the given elements without
delving into layout:include, layout:replace, or
layout:substituteby elements.
Marks sections of the template that can be replaced by sections in the
content template (if decorating) or passed along to included pages (if
including), which share the same name.
The same as pullAttributes(Element, Element), but with the
option to specify whether to copy everything over, or only attributes
that already exist in sourceelement.