docs: def _make_attr_element(parent, attr_i):
      """
          create an attribute element from an attribute DB object
      """
      attr = etree.SubElement(parent, "attribute")
  
      attr_name      = etree.SubElement(attr, 'name')
      attr_name.text = attr_i.name
  
      attr_desc      = etree.SubElement(attr, 'description')
      attr_desc.text = attr_i.description
  
      attr_dimension = etree.SubElement(attr, 'dimension')
      attr_dimension.text = units.get_dimension(attr_i.dimension_id, do_accept_dimension_id_none=True).name
  
      return attr