code: private Map<String, Object> readHeaderElements(AdManagerSession adManagerSession) {
      // The order here must match the order of the SoapRequestHeader elements in the WSDL.
      Map<String, Object> mapToFill = Maps.newLinkedHashMap();
      mapToFill.put("networkCode", adManagerSession.getNetworkCode());
      mapToFill.put(
          "applicationName", userAgentCombiner.getUserAgent(adManagerSession.getApplicationName()));
      return mapToFill;
    }
docs: Creates a map with data from the user's service session which is needed to set Ad Manager SOAP
  headers.
  
  @param adManagerSession the user's session object
  @return a map of HTTP header names to values