code: public FieldsFilter withFields(String fields, boolean includeFields) {
          parameters.put("fields", fields);
          parameters.put("include_fields", includeFields);
          return this;
      }
docs: Only retrieve certain fields from the item.
  
  @param fields        a list of comma separated fields to retrieve.
  @param includeFields whether to include or exclude in the response the fields that were given.
  @return this filter instance