How to implement service in a class in rospy with no args?

edit

I'm trying to implement a service on Kinetic (no args, two return values) but I am getting the error:

service [/classify_container] responded with an error: error processing request: classify_container() takes exactly 1 argument (2 given)

Where am I going wrong?

Classification.srv

---
string class_name
float32 confidence

The Service

from pytorch_ros.srv import Classification

class PytorchNode(object):
    def __init__(self):
        classification_service = rospy.Service('classify',
                                               Classification,
                                               self.classify_handle)

    def classify_handle(self):
        # do some stuff
        # to get the classification
        # .....

        # construct msg and return
        classification_msg = Classification()
        classification_msg.class_name = self.names[classification]
        classification_msg.confidence = confidence

        return classification_msg

The client

  #!/usr/bin/env python
  from __future__ import division
  from __future__ import print_function

  import rospy 
  from pytorch_ros.srv import Classification

  rospy.wait_for_service('classify_container')

  try:
      srv_classify_container = rospy.ServiceProxy('classify_container', Classification)
      classification = srv_classify_container()
      print(classification.class_name)
      print(classification.confidence)
  except rospy.ServiceException as e:
      print("Service call failed: %s" % e)