code: @Override
    public Collection<ConfigKeyPath> getImportedBy(ConfigKeyPath configKey) {
      return getImportedBy(configKey, Optional.<Config>absent());
    }
docs: {@inheritDoc}.
  
  <p>
  If the result is already in cache, return the result.
  Otherwise, delegate the functionality to the fallback object.
  
  If the fallback did not support this operation, will build the entire topology of the {@link org.apache.gobblin.config.store.api.ConfigStore}
  using default breath first search.
  </p>