code: @Override
    public Iterator<Entry<String, Fetch>> iterator() {
      return Collections.unmodifiableMap(attrFetchMap).entrySet().iterator();
    }
docs: Iterates over all fields in this fetch. The key is the field name, the value is the {@link
  Fetch} for that field, or null if no Fetch is provided for that field.
  
  @return {@link Iterator} over all {@link Entry}s in this fetch.