code: protected void addFacetPart(CmsSolrQuery query) {
  
          StringBuffer value = new StringBuffer();
          value.append("{!key=").append(m_config.getName());
          addFacetOptions(value);
          if (m_config.getIgnoreAllFacetFilters()
              || (!m_state.getCheckedEntries().isEmpty() && !m_config.getIsAndFacet())) {
              value.append(" ex=").append(m_config.getIgnoreTags());
          }
          value.append("}");
          value.append(m_config.getRange());
          query.add("facet.range", value.toString());
      }
docs: Generate query part for the facet, without filters.
  @param query The query, where the facet part should be added