docs: public boolean existsCollection(String collectionName) throws SolrException {
          try {
              List<String> collections = CollectionAdminRequest.listCollections(solrClient);
              for (String collection : collections) {
                  if (collection.equals(collectionName)) {
                      return true;
                  }
              }
              return false;
          } catch (Exception e) {
              throw new SolrException(SolrException.ErrorCode.CONFLICT, e);
          }
      }