code: public String toVoJSONString() {
          if (context.isPretty()) {
              return JSON.toJSONStringWithDateFormat(toVoJSONObject(), Constant.DATE_SERIALIZE_FORMAT, SerializerFeature.PrettyFormat);
          } else {
              return JSONObject.toJSONStringWithDateFormat(toVoJSONObject(), Constant.DATE_SERIALIZE_FORMAT);
          }
      }
docs: Our api gateway uses this method instead of {@link #toJSONString()} {@link #toString()} to produce a desensitized output VO json string.
  For detail, see the return description.
  
  @return json string with sensitive properties(the context property) hidden.