code: @Override
      public Map<String, String> getValues() {
          HashMap<String, String> result = new HashMap<>();
  
          if (status != null && status != MandateStatus.NotSpecified) {
              result.put("status", status.name());
          }
  
          if (beforeDate != null) result.put("beforeDate", Long.toString(beforeDate));
          if (afterDate != null) result.put("afterDate", Long.toString(afterDate));
  
          return result;
      }
docs: Gets map of fields and values.
  
  @return Collection of field name-field value pairs.