docs: public void marshall(User user, ProtocolMarshaller protocolMarshaller) {
  
          if (user == null) {
              throw new SdkClientException("Invalid argument passed to marshall(...)");
          }
  
          try {
              protocolMarshaller.marshall(user.getArn(), ARN_BINDING);
              protocolMarshaller.marshall(user.getUserName(), USERNAME_BINDING);
              protocolMarshaller.marshall(user.getEnabled(), ENABLED_BINDING);
              protocolMarshaller.marshall(user.getStatus(), STATUS_BINDING);
              protocolMarshaller.marshall(user.getFirstName(), FIRSTNAME_BINDING);
              protocolMarshaller.marshall(user.getLastName(), LASTNAME_BINDING);
              protocolMarshaller.marshall(user.getCreatedTime(), CREATEDTIME_BINDING);
              protocolMarshaller.marshall(user.getAuthenticationType(), AUTHENTICATIONTYPE_BINDING);
          } catch (Exception e) {
              throw new SdkClientException("Unable to marshall request to JSON: " + e.getMessage(), e);
          }
      }