code: public RESTParameter add(RESTParameter childParam) {
          Utils.require(!Utils.isEmpty(childParam.getName()), "Child parameter name cannot be empty");
          m_parameters.add(childParam);
          return this;
      }
docs: Add the given RESTParameter as a child of this parameter. This parameter is
  returned to support builder syntax.
  
  @param childParam    New child RESTParameter of this parameter. The child parameter
  name must be unique.
  @return              This parameter object.