code: def _convertToElementList(elements_list):
      
      elements = []
      current_element = []
      for node_index in elements_list:
          if node_index == -1:
              elements.append(current_element)
              current_element = []
          else:
              current_element.append(node_index)
  
      return elements
docs: Take a list of element node indexes deliminated by -1 and convert
      it into a list element node indexes list.