void put(K key, V value) {
      Collection<V> valueContainer = delegate.get(key);
      if (valueContainer == null) {
        delegate.put(key, valueContainer = valueContainer());
      }
      if (valueContainer.add(value)) size++;
    }
Returns service names orphaned by removing the trace ID
zipkin/src/main/java/zipkin2/storage/InMemoryStorage.java