public Builder retainDimensions(Collection<DimensionId> idsToRetain) {
            dimensions.keySet().retainAll(idsToRetain);
            return this;
        }
Returns a modifiable copy of the dimension IDs of this builder, usually for use with {@link #retainDimensions(Collection)}.
metrics-proxy/src/main/java/ai/vespa/metricsproxy/metric/model/MetricsPacket.java