new_contents: try:
      import ujson as json
  except ImportError:
      import json
  import mock
  from unittest import TestCase
  from devour.handlers import _ProducerProxy
  
  
  class TestProducerProxy(TestCase):
      def test_produce_called_with_proper_args(self):
          producer = mock.MagicMock()
          proxy = _ProducerProxy(producer)
  
          proxy.produce('message', 'partition_key')
          producer.produce.assert_called_once_with(json.dumps('message'), 'partition_key')
  
subject: Add producer proxy test