@VisibleForTesting
  static ImmutableSet<AbsoluteUnixPath> volumeMapToSet(
      @Nullable Map<String, Map<String, String>> volumeMap)
      throws BadContainerConfigurationFormatException {
    if (volumeMap == null) {
      return ImmutableSet.of();
    }

    ImmutableSet.Builder<AbsoluteUnixPath> volumeList = ImmutableSet.builder();
    for (String volume : volumeMap.keySet()) {
      try {
        volumeList.add(AbsoluteUnixPath.get(volume));
      } catch (IllegalArgumentException exception) {
        throw new BadContainerConfigurationFormatException("Invalid volume path: " + volume);
      }
    }

    return volumeList.build();
  }
Converts a map of volumes strings to a set of {@link AbsoluteUnixPath}s (e.g. {@code
{"/var/log/my-app-logs":{}}} -> {@code AbsoluteUnixPath().get("/var/log/my-app-logs")}).

@param volumeMap the map to convert
@return a set of {@link AbsoluteUnixPath}s
jib-core/src/main/java/com/google/cloud/tools/jib/image/json/JsonToImageTranslator.java