code: public CheckMethod getCheckMethod(String fieldName) {
          CheckMethod method = checkMethods.get(fieldName);
          if(method==null) {
              method = new CheckMethod(this,fieldName);
              checkMethods.put(fieldName,method);
          }
  
          return method;
      }
docs: If the field "xyz" of a {@link Describable} has the corresponding "doCheckXyz" method,
  return the model of the check method.
  <p>
  This method is used to hook up the form validation method to the corresponding HTML input element.