FieldError: Cannot resolve keyword 'system' into field. Choices are: attribute, entity, id, value

[zeeman]

import urllib
import urllib2

MY_TOKEN = Token

def api_connect(url, params=None):
    if params:
        url += "?" + urllib.urlencode(params)
    req = urllib2.Request(url)
    req.add_header('Authorization', 'Token ' + MY_TOKEN)
    return urllib2.urlopen(req).read()

query = {'a:operating+system': 'linux'}
print api_connect("http://127.0.0.1:8000/api/v1/core/system/", query)

[zeeman]

Environment:

Request Method: GET
Request URL: http://127.0.0.1:8000/api/v1/core/system/?a%3Aoperating%2Bsystem=linux

Django Version: 1.4.1
Python Version: 2.7.4
Installed Applications:
['funfactory',
'compressor',
'tower',
'cronjobs',
'django_browserid',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.staticfiles',
'commonware.response.cookies',
'djcelery',
'django_nose',
'session_csrf',
'product_details',
'cyder',
'south',
'django_cas',
'djcelery',
'django_extensions',
'django_nose',
'jingo_minify',
'rest_framework',
'django.contrib.sessions',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.admin',
'django.contrib.messages']
Installed Middleware:
('django.middleware.common.CommonMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'cyder.middleware.dev_authentication.DevAuthenticationMiddleware')

Traceback:
File "/home/zane/cyder-test/cyder/vendor/lib/python/django/core/handlers/base.py" in get_response
111.                         response = callback(request, *callback_args, **callback_kwargs)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/viewsets.py" in view
78.             return self.dispatch(request, *args, **kwargs)
File "/home/zane/cyder-test/cyder/vendor/lib/python/django/views/decorators/csrf.py" in wrapped_view
77.         return view_func(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/views.py" in dispatch
399.             response = self.handle_exception(exc)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/views.py" in dispatch
396.             response = handler(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/mixins.py" in list
74.         self.object_list = self.filter_queryset(self.get_queryset())
File "/usr/local/lib/python2.7/dist-packages/rest_framework/generics.py" in filter_queryset
179.             queryset = backend().filter_queryset(self.request, queryset, self)
File "/home/zane/cyder-test/cyder/cyder/api/v1/filter.py" in filter_queryset
99.                 parent_ids = reduce((lambda x, y: x & y), parent_set_list)
File "/home/zane/cyder-test/cyder/cyder/api/v1/filter.py" in <genexpr>
98.                     matching(k, q_attributes[k]) for k in q_attributes)
File "/home/zane/cyder-test/cyder/cyder/api/v1/filter.py" in <lambda>
93.                         flat=True
File "/home/zane/cyder-test/cyder/vendor/lib/python/django/db/models/query.py" in values_list
585.                 _fields=fields)
File "/home/zane/cyder-test/cyder/vendor/lib/python/django/db/models/query.py" in _clone
864.             c._setup_query()
File "/home/zane/cyder-test/cyder/vendor/lib/python/django/db/models/query.py" in _setup_query
988.         self.query.add_fields(self.field_names, True)
File "/home/zane/cyder-test/cyder/vendor/lib/python/django/db/models/sql/query.py" in add_fields
1669.                     "Choices are: %s" % (name, ", ".join(names)))

Exception Type: FieldError at /api/v1/core/system/
Exception Value: Cannot resolve keyword 'system' into field. Choices are: attribute, entity, id, value