MedCAT Trainer -- cannot export JSON CUI filter

MedCAT
1

When trying to download a concerpt filter JSON from the concepts tab I get this error:

[medcattrainer] Internal Server Error: /api/generate-concept-filter-json/
[medcattrainer] Traceback (most recent call last):
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/django/core/handlers/exception.py", line 55, in inner
[medcattrainer]     response = get_response(request)
[medcattrainer]                ^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/django/core/handlers/base.py", line 197, in _get_response
[medcattrainer]     response = wrapped_callback(request, *callback_args, **callback_kwargs)
[medcattrainer]                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/django/views/decorators/csrf.py", line 65, in _view_wrapper
[medcattrainer]     return view_func(request, *args, **kwargs)
[medcattrainer]            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/django/views/generic/base.py", line 105, in view
[medcattrainer]     return self.dispatch(request, *args, **kwargs)
[medcattrainer]            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/rest_framework/views.py", line 515, in dispatch
[medcattrainer]     response = self.handle_exception(exc)
[medcattrainer]                ^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/rest_framework/views.py", line 475, in handle_exception
[medcattrainer]     self.raise_uncaught_exception(exc)
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/rest_framework/views.py", line 486, in raise_uncaught_exception
[medcattrainer]     raise exc
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/rest_framework/views.py", line 512, in dispatch
[medcattrainer]     response = handler(request, *args, **kwargs)
[medcattrainer]                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/rest_framework/decorators.py", line 50, in handler
[medcattrainer]     return func(*args, **kwargs)
[medcattrainer]            ^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/api/api/views.py", line 1076, in generate_concept_filter_flat_json
[medcattrainer]     filter_json = json.dumps(final_filter)
[medcattrainer]                   ^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/usr/local/lib/python3.12/json/__init__.py", line 231, in dumps
[medcattrainer]     return _default_encoder.encode(obj)
[medcattrainer]            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/usr/local/lib/python3.12/json/encoder.py", line 200, in encode
[medcattrainer]     chunks = self.iterencode(o, _one_shot=True)
[medcattrainer]              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/usr/local/lib/python3.12/json/encoder.py", line 258, in iterencode
[medcattrainer]     return _iterencode(o, 0)
[medcattrainer]            ^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/usr/local/lib/python3.12/json/encoder.py", line 180, in default
[medcattrainer]     raise TypeError(f'Object of type {o.__class__.__name__} '
[medcattrainer] TypeError: Object of type dict_keys is not JSON serializable
[medcattrainer] ERROR 2026-05-09 12:49:26,005 log.py l:253:Internal Server Error: /api/generate-concept-filter-json/
[medcattrainer] Traceback (most recent call last):
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/django/core/handlers/exception.py", line 55, in inner
[medcattrainer]     response = get_response(request)
[medcattrainer]                ^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/django/core/handlers/base.py", line 197, in _get_response
[medcattrainer]     response = wrapped_callback(request, *callback_args, **callback_kwargs)
[medcattrainer]                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/django/views/decorators/csrf.py", line 65, in _view_wrapper
[medcattrainer]     return view_func(request, *args, **kwargs)
[medcattrainer]            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/django/views/generic/base.py", line 105, in view
[medcattrainer]     return self.dispatch(request, *args, **kwargs)
[medcattrainer]            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/rest_framework/views.py", line 515, in dispatch
[medcattrainer]     response = self.handle_exception(exc)
[medcattrainer]                ^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/rest_framework/views.py", line 475, in handle_exception
[medcattrainer]     self.raise_uncaught_exception(exc)
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/rest_framework/views.py", line 486, in raise_uncaught_exception
[medcattrainer]     raise exc
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/rest_framework/views.py", line 512, in dispatch
[medcattrainer]     response = handler(request, *args, **kwargs)
[medcattrainer]                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/.venv/lib/python3.12/site-packages/rest_framework/decorators.py", line 50, in handler
[medcattrainer]     return func(*args, **kwargs)
[medcattrainer]            ^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/home/api/api/views.py", line 1076, in generate_concept_filter_flat_json
[medcattrainer]     filter_json = json.dumps(final_filter)
[medcattrainer]                   ^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/usr/local/lib/python3.12/json/__init__.py", line 231, in dumps
[medcattrainer]     return _default_encoder.encode(obj)
[medcattrainer]            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/usr/local/lib/python3.12/json/encoder.py", line 200, in encode
[medcattrainer]     chunks = self.iterencode(o, _one_shot=True)
[medcattrainer]              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/usr/local/lib/python3.12/json/encoder.py", line 258, in iterencode
[medcattrainer]     return _iterencode(o, 0)
[medcattrainer]            ^^^^^^^^^^^^^^^^^
[medcattrainer]   File "/usr/local/lib/python3.12/json/encoder.py", line 180, in default
[medcattrainer]     raise TypeError(f'Object of type {o.__class__.__name__} '
[medcattrainer] TypeError: Object of type dict_keys is not JSON serializable

Root cause: After deduplicating the concept list, final_filter ends up as a dict_keys object (not a plain list). json.dumps() can’t serialise dict_keys, so it crashes.

File: webapp/api/api/views.py line 1086

Before: filter_json = json.dumps(final_filter)

Patch: filter_json = json.dumps(list(final_filter))

Happy to help create pull request if helpful.

2

Thanks for the feedback!

Yes, this does look like an issue ineed.

And the fix you’ve outlined seems decent as well. So if you don’t mind pushing that as a PR as well, we’d really appreciate it!