code: public void validate(@Nullable String version) {
      if (reportDownloadTimeout != null) {
        Preconditions.checkArgument(
            reportDownloadTimeout >= 0, "Report download timeout is < 0: %s", reportDownloadTimeout);
      }
    }
docs: Validates this object for the specified version of the AdWords API.
  
  @param version the {@code v20YYMM} version of the API to validate against.
  @throws IllegalArgumentException if validation fails