code: def getInstancePid(topology_info, instance_id):
    
    try:
      http_client = tornado.httpclient.AsyncHTTPClient()
      endpoint = utils.make_shell_endpoint(topology_info, instance_id)
      url = "%s/pid/%s" % (endpoint, instance_id)
      Log.debug("HTTP call for url: %s", url)
      response = yield http_client.fetch(url)
      raise tornado.gen.Return(response.body)
    except tornado.httpclient.HTTPError as e:
      raise Exception(str(e))
docs: This method is used by other modules, and so it
    is not a part of the class.
    Fetches Instance pid from heron-shell.