docs: protected TableSchema getSchema() {
      List<TableFieldSchema> fields = new ArrayList<>();
      for (Map.Entry<String, FieldInfo<InputT>> entry : fieldInfo.entrySet()) {
        String key = entry.getKey();
        FieldInfo<InputT> fcnInfo = entry.getValue();
        String bqType = fcnInfo.getFieldType();
        fields.add(new TableFieldSchema().setName(key).setType(bqType));
      }
      return new TableSchema().setFields(fields);
    }