private void removeFromAttributePrefetchSummaryClass(SDField field) {
        DocumentSummary summary = schema.getSummariesInThis().get(SORTABLE_ATTRIBUTES_SUMMARY_CLASS);
        if (summary != null) {
            summary.remove(field.getName());
        }
    }
Class that processes reference fields and removes attribute aspect of such fields from summary.

A document summary for a reference field should always be fetched from the document instance in back-end
as the attribute vector does not store the original document id string.

@author geirst
config-model/src/main/java/com/yahoo/schema/processing/ReferenceFieldsProcessor.java