docs: def parse_on_event(self, node):
          """
          Parses <OnEvent>
  
          @param node: Node containing the <OnEvent> element
          @type node: xml.etree.Element
          """
  
          try:
              port = node.lattrib['port']
          except:
              self.raise_error('<OnEvent> must specify a port.')
              
          event_handler = OnEvent(port)
  
          self.current_regime.add_event_handler(event_handler)
  
          self.current_event_handler = event_handler
          self.process_nested_tags(node)
          self.current_event_handler = None