@Override
    public int hashCode() {
        return Objects.hash(super.hashCode(),
                description,
                collection,
                solrConnectionConfig,
                fields,
                timeField,
                defaultExtractionPipeline);
    }
@return A new builder for creating a {@link DocRef} for this document's type.
stroom-core-shared/src/main/java/stroom/search/solr/shared/SolrIndexDoc.java