code: @Override
    public String toFormattedString(Field f) throws IOException {
      return this.getClass().getName() + " " + f.name();
    }
docs: /*
  (non-Javadoc)
  
  @see
  org.apache.solr.schema.PreAnalyzedField.PreAnalyzedParser#toFormattedString
  (org.apache.lucene.document.Field)