docs: def init_ixn(api, logger, install_dir=None):
      """ Create IXN object.
  
      :param api: tcl/python/rest
      :type api: trafficgenerator.tgn_utils.ApiType
      :param logger: logger object
      :param install_dir: IXN installation directory
      :return: IXN object
      """
  
      if api == ApiType.tcl:
          api_wrapper = IxnTclWrapper(logger, install_dir)
      elif api == ApiType.python:
          api_wrapper = IxnPythonWrapper(logger, install_dir)
      elif api == ApiType.rest:
          api_wrapper = IxnRestWrapper(logger)
      else:
          raise TgnError('{} API not supported - use Tcl, python or REST'.format(api))
      return IxnApp(logger, api_wrapper)