def element_parents_recursive(sequence)
      parents = Array.new
      sequence.items.each do |i|
        parents << i if i.elements?
        i.sequences.each do |s|
          parents += element_parents_recursive(s)
        end
      end
      parents
    end
def element_parents_recursive(sequence)
      parents = Array.new
      sequence.items.each do |i|
        parents << i if i.elements?
        i.sequences.each do |s|
          parents += element_parents_recursive(s)
        end
      end
      parents
    end
Recursively extracts all item parents from a sequence instance (including
 any sub-sequences) which actually contain child (data) elements.

 @param [Sequence] sequence a Sequence instance
 @return [Array<Item>] an array containing items within the tag hierarchy that contains child elements