out (ret)
{
assert ((cast(DocumentFragment)this !is null) || (e.parentNode is this), e.toString);
assert (e.parentDocument is this.parentDocument);
assert (e is ret);
}
Prior to 1 Jan 2020 (git tag v4.4.1 and below), it required that the given element must not have a parent already. This was in violation of standard, so it changed the behavior to remove it from the existing parent and instead move it here.
Appends the given element to this one. If it already has a parent, it is removed from that tree and moved to this one.