docs: public static String queryToExpressionStr(ServiceInstanceQuery query){
          List<QueryCriterion> criteria = query.getCriteria();
          StringBuilder sb = new StringBuilder();
          for(QueryCriterion criterion : criteria){
              String statement = criterionToExpressionStr(criterion);
              if(statement != null && ! statement.isEmpty()){
                  sb.append(statement).append(";");
              }
          }
          return sb.toString();
      }