def deserialize_json(stream, username):
    """
    Given a stream containing JSON, deserializers the JSON into ConfigurationModel instances.

    The stream is expected to be in the following format:
        { "model": "config_models.ExampleConfigurationModel",
          "data":
            [
              { "enabled": True,
                "color": "black"
                ...
              },
              { "enabled": False,
                "color": "yellow"
                ...
              },
              ...
            ]
        }

    If the provided stream does not contain valid JSON for the ConfigurationModel specified,
    an Exception will be raised.

    Arguments:
            stream: The stream of JSON, as described above.
            username: The username of the user making the change. This must match an existing user.

    Returns: the number of created entries
    """
    parsed_json = JSONParser().parse(stream)
    serializer_class = get_serializer_class(apps.get_model(parsed_json["model"]))
    list_serializer = serializer_class(data=parsed_json["data"], context={"changed_by_username": username}, many=True)
    if list_serializer.is_valid():
        model_class = serializer_class.Meta.model
        for data in reversed(list_serializer.validated_data):
            if model_class.equal_to_current(data):
                list_serializer.validated_data.remove(data)

        entries_created = len(list_serializer.validated_data)
        list_serializer.save()
        return entries_created
    else:
        raise Exception(list_serializer.error_messages)