public Builder addLabels(@Nullable Map<String, String> labels) {
      if (labels != null) {
        labelsBuilder.putAll(labels);
      }
      return this;
    }
Adds items to the "Labels" field in the container configuration.

@param labels the map of labels to add
@return this
jib-core/src/main/java/com/google/cloud/tools/jib/image/Image.java