@Override
    public String toString() {
        return "SolrIndex{" +
               "description='" + description + '\'' +
               ", collection='" + collection + '\'' +
               ", solrConnectionConfig=" + solrConnectionConfig +
               ", fields=" + fields +
               ", timeField=" + timeField +
               ", defaultExtractionPipeline=" + 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