Object of type 'Action' is not JSON serializable

I have the following relationships between my Action and my User models :

class Action(Model):
    members = models.ManyToManyField(User, blank=True, related_name='actions')

I would like to filter the old action :

def active_actions(self):
    return self.actions.filter(date__gte=date.today())
User.active_actions=active_actions

Traceback :

Environment:


Request Method: GET
Request URL: http://127.0.0.1:8000/api/users/2/

Django Version: 1.11.21
Python Version: 3.6.7
Installed Applications:
['risefor-mobilisation',
 'data_manager',
 'djangoldp_conversation',
 'django_extensions',
 'djangoldp',
 'guardian',
 'registration',
 'django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware']



Traceback:

File "/home/alex/.local/lib/python3.6/site-packages/django/core/handlers/exception.py" in inner
  41.             response = get_response(request)

File "/home/alex/.local/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  217.                 response = self.process_exception_by_middleware(e, request)

File "/home/alex/.local/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  215.                 response = response.render()

File "/home/alex/.local/lib/python3.6/site-packages/django/template/response.py" in render
  107.             self.content = self.rendered_content

File "/home/alex/.local/lib/python3.6/site-packages/rest_framework/response.py" in rendered_content
  72.         ret = renderer.render(self.data, accepted_media_type, context)

File "/var/www/risefor-mobilisation/djangoldp/views.py" in render
  27.         return super(JSONLDRenderer, self).render(data, accepted_media_type, renderer_context)

File "/home/alex/.local/lib/python3.6/site-packages/rest_framework/renderers.py" in render
  107.             allow_nan=not self.strict, separators=separators

File "/home/alex/.local/lib/python3.6/site-packages/rest_framework/utils/json.py" in dumps
  28.     return json.dumps(*args, **kwargs)

File "/usr/lib/python3.6/json/__init__.py" in dumps
  238.         **kw).encode(obj)

File "/usr/lib/python3.6/json/encoder.py" in encode
  199.         chunks = self.iterencode(o, _one_shot=True)

File "/usr/lib/python3.6/json/encoder.py" in iterencode
  257.         return _iterencode(o, 0)

File "/home/alex/.local/lib/python3.6/site-packages/rest_framework/utils/encoders.py" in default
  68.         return super(JSONEncoder, self).default(obj)

File "/usr/lib/python3.6/json/encoder.py" in default
  180.                         o.__class__.__name__)

Exception Type: TypeError at /api/users/2/
Exception Value: Object of type 'Action' is not JSON serializable