code: def _to_DOM(self):
          
          root_node = ET.Element("ozone")
          reference_time_node = ET.SubElement(root_node, "reference_time")
          reference_time_node.text = str(self._reference_time)
          reception_time_node = ET.SubElement(root_node, "reception_time")
          reception_time_node.text = str(self._reception_time)
          interval_node = ET.SubElement(root_node, "interval")
          interval_node.text = str(self._interval)
          value_node = ET.SubElement(root_node, "value")
          value_node.text = str(self.du_value)
          root_node.append(self._location._to_DOM())
          return root_node
docs: Dumps object data to a fully traversable DOM representation of the
          object.
  
          :returns: a ``xml.etree.Element`` object