Single Cell Datasets: problems with loading datasets

[elapraznik]

Describe the bug
When I try to load particular single-cell datasets available through the Single Cell Datasets widget I get an error message (cases 1.-4.). One dataset (5. case) takes a very long time to load (especially in comparison to some larger datasets). The particular datasets and the problem encountered are as follows:

1. Pancreas cells in mouse - error when trying to load
2. Human osteoarthritis chondrocytes - error when trying to load
3. Stimulated and resting immune cells (3000 cells) - error when trying to load
4. Human preimplantation embryos - error when trying to load
5. Mouse retinal bipolar neurons (DropSeq, large) - needs several minutes to load, size 10.7MB (larger files, e.g. 23MB, take less time to load)

To Reproduce
Steps to reproduce the behavior:

1. Go to Orange canvas and open Single Cell Datasets widget
2. Click on the listed problematic datasets

Screenshots
When trying to load the first four datasets (1.-4.), I get an error message (same for all four):

Traceback (most recent call last):
File "/opt/miniconda3/envs/orange3/lib/python3.10/site-packages/Orange/widgets/data/owdatasets.py", line 605, in __commit_complete
self.load_and_output(path)
File "/opt/miniconda3/envs/orange3/lib/python3.10/site-packages/Orange/widgets/data/owdatasets.py", line 636, in load_and_output
data = self.load_data(path)
File "/opt/miniconda3/envs/orange3/lib/python3.10/site-packages/orangecontrib/single_cell/widgets/owscdatasets.py", line 38, in load_data
data = Orange.data.Table(path)
File "/opt/miniconda3/envs/orange3/lib/python3.10/site-packages/Orange/data/table.py", line 713, in new
return cls.from_file(args[0], **kwargs)
File "/opt/miniconda3/envs/orange3/lib/python3.10/site-packages/Orange/data/table.py", line 1104, in from_file
data = reader.read()
File "/opt/miniconda3/envs/orange3/lib/python3.10/site-packages/Orange/data/io.py", line 208, in read
table = pickle.load(f)
File "/opt/miniconda3/envs/orange3/lib/python3.10/site-packages/Orange/data/variable.py", line 38, in make_variable
return cls(*args, compute_value=compute_value)
TypeError: DiscreteVariable.init() got multiple values for argument 'compute_value'

Desktop (please complete the following information):

• OS: macOS Monterey
• Python Version: 3.10
• Orange Version: 3.36.2
• Add-on Version: Single Cell Add-on 1.5.0