docs: public List<IndexableField> postProcessingIndexableFields(Columns columns, Search search) {
          List<IndexableField> fields = new LinkedList<>();
          search.postProcessingFields().forEach(field -> {
              Mapper mapper = mapper(field);
              if (mapper != null) {
                  fields.addAll(mapper.indexableFields(columns));
              }
          });
          return fields;
      }