# File TagTreeScanner.rb, line 472
                def remove_child( existing_child )
                        idx = @child_tags.index( existing_child )
                        raise "#{existing_child.inspect} is not a child of #{self.inspect}" unless idx
                        prev, succ = existing_child.previous_sibling, existing_child.next_sibling
                        prev.next_sibling = succ if prev
                        succ.previous_sibling = prev if succ
                        @child_tags.delete_at( idx )
                        existing_child.previous_sibling = existing_child.next_sibling = existing_child.parent_tag = nil
                        existing_child
                end