code: def addIndex(self, ticker, name):
      symbolElement = etree.Element("symbol")
      symbolElement.set("ticker", ticker)
      symbolElement.set("name", name)
      symbolElement.set("type", "index")
      self.__root.append(symbolElement)
  
file_path: pyalgotrade/tools/symbols/symbolsxml.py
imports: from lxml import etree
label_desc: Use image node_id 3 for calling the Writer obj's underlying member method code with example usage: obj.addIndex(ticker, name) without return types