TypeError: Expected a 'coreapi.Document' instance

[dengsibao]

my env:
python 3.6
django 3.0.4
django-rest-swagger 2.2.0
djangorestframework 3.11.0

error:
Internal Server Error: /docs/ Traceback (most recent call last): File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/django/core/handlers/exception.py", line 34, in inner response = get_response(request) File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/django/core/handlers/base.py", line 145, in _get_response response = self.process_exception_by_middleware(e, request) File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/django/core/handlers/base.py", line 143, in _get_response response = response.render() File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/django/template/response.py", line 106, in render self.content = self.rendered_content File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/rest_framework/response.py", line 70, in rendered_content ret = renderer.render(self.data, accepted_media_type, context) File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/rest_framework_swagger/renderers.py", line 54, in render self.set_context(data, renderer_context) File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/rest_framework_swagger/renderers.py", line 70, in set_context renderer_context=renderer_context File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/rest_framework_swagger/renderers.py", line 34, in render return OpenAPICodec().encode(data, **options) File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/rest_framework_swagger/renderers.py", line 16, in encode raise TypeError('Expected a coreapi.Documentinstance') TypeError: Expected acoreapi.Documentinstance