создание модели Django, которая имеет отношение к своему классу

Question

Я хочу создать модель под названием задача, у нее есть несколько полей и связь с самим собой, это означает, что сама задача может быть создана из некоторых других задач, код:

from django.db import models

class Task(models.Model):
    name = models.CharField(max_length=100)
    ...
    ...
    tasks = models.ForeignKey(Task, on_delete=models.CASCADE, blank=True)

    def __str__(self):
        return self.name

, а затем django показываетошибки, что Задача не определена:

/home/hamex/currect/myBlog/main/task/models.py changed, reloading.
Watching for file changes with StatReloader
Exception in thread django-main-thread:
Traceback (most recent call last):
  File "/usr/lib/python3.6/threading.py", line 916, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.6/threading.py", line 864, in run
    self._target(*self._args, **self._kwargs)
  File "/home/hamex/virtualPyEviors/django2/lib/python3.6/site-packages/django/utils/autoreload.py", line 54, in wrapper
    fn(*args, **kwargs)
  File "/home/hamex/virtualPyEviors/django2/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 109, in inner_run
    autoreload.raise_last_exception()
  File "/home/hamex/virtualPyEviors/django2/lib/python3.6/site-packages/django/utils/autoreload.py", line 77, in raise_last_exception
    raise _exception[1]
  File "/home/hamex/virtualPyEviors/django2/lib/python3.6/site-packages/django/core/management/__init__.py", line 337, in execute
    autoreload.check_errors(django.setup)()
  File "/home/hamex/virtualPyEviors/django2/lib/python3.6/site-packages/django/utils/autoreload.py", line 54, in wrapper
    fn(*args, **kwargs)
  File "/home/hamex/virtualPyEviors/django2/lib/python3.6/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/home/hamex/virtualPyEviors/django2/lib/python3.6/site-packages/django/apps/registry.py", line 114, in populate
    app_config.import_models()
  File "/home/hamex/virtualPyEviors/django2/lib/python3.6/site-packages/django/apps/config.py", line 211, in import_models
    self.models_module = import_module(models_module_name)
  File "/usr/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/hamex/currect/myBlog/main/task/models.py", line 14, in <module>
    class Task(models.Model):
  File "/home/hamex/currect/myBlog/main/task/models.py", line 23, in Task
    testwithselffor = models.ForeignKey(Task, blank=True, on_delete=models.CASCADE)
NameError: name 'Task' is not defined

я делаю что-то не так ??а может это не правильный способ решить эту проблему ??