code: @Override
    public Collection<ConfigKeyPath> getChildren(ConfigKeyPath configKey) {
      try {
        return this.childrenMap.get(configKey, () -> this.fallback.getChildren(configKey));
      } catch (ExecutionException ee) {
        throw new RuntimeException(ee);
      }
    }
docs: {@inheritDoc}.
  
  <p>
  If the result is already in cache, return the result.
  Otherwise, delegate the functionality to the fallback object
  </p>