AttributeError: 'module' object has no attribute 'SubfieldBase'

I'm working on a project that was built using an earlier version of django. My environment has the latest Django version (1.11.4). 

When I try to "python manage.py runserver" I get this: 

Unhandled exception in thread started by <function wrapper at 0x7fb1dab36cf8>

Traceback (most recent call last):

  File "/usr/local/lib/python2.7/dist-packages/django/utils/autoreload.py", line 228, in wrapper

    fn(*args, **kwargs)

  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/runserver.py", line 117, in inner_run

    autoreload.raise_last_exception()

  File "/usr/local/lib/python2.7/dist-packages/django/utils/autoreload.py", line 251, in raise_last_exception

    six.reraise(*_exception)

  File "/usr/local/lib/python2.7/dist-packages/django/utils/autoreload.py", line 228, in wrapper

    fn(*args, **kwargs)

  File "/usr/local/lib/python2.7/dist-packages/django/__init__.py", line 27, in setup

    apps.populate(settings.INSTALLED_APPS)

  File "/usr/local/lib/python2.7/dist-packages/django/apps/registry.py", line 108, in populate

    app_config.import_models()

  File "/usr/local/lib/python2.7/dist-packages/django/apps/config.py", line 202, in import_models

    self.models_module = import_module(models_module_name)

  File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module

    __import__(name)

  File "/home/ahmedn1/Documents/Paymob/wallet_executive_panel-master-c109bd6fe9cd1bf793c11a5c2e97d18a1887c3ba/accounts/models.py", line 8, in <module>

    import timedelta

  File "/usr/local/lib/python2.7/dist-packages/timedelta/__init__.py", line 11, in <module>

    from .fields import TimedeltaField

  File "/usr/local/lib/python2.7/dist-packages/timedelta/fields.py", line 18, in <module>

    class TimedeltaField(six.with_metaclass(models.SubfieldBase, models.Field)):

AttributeError: 'module' object has no attribute 'SubfieldBase'

So the problem is with the django-timedeltafield package but its version is 0.7.10 which is the latest version. So, why does it still have a problem with this deprecated SubfieldBase? 

What should I do to solve the problem?  

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