Dataset.to_dict_of_arrays raises an AttributedError when by_group and by_entry are True

The lines

d = create_benchmark_dataset("IrisDataset")
d.to_dict_of_arrays(True, True)

raises an AttributeError:

Traceback (most recent call last):
  File "C:\Users\matthias.delozzo\AppData\Local\JetBrains\PyCharm Community Edition 2023.1\plugins\python-ce\helpers\pydev\pydevconsole.py", line 364, in runcode
    coro = func()
  File "<input>", line 1, in <module>
  File "C:\Users\matthias.delozzo\workspace\GEMSEO\gemseo\src\gemseo\datasets\dataset.py", line 1052, in to_dict_of_arrays
    return [
  File "C:\Users\matthias.delozzo\workspace\GEMSEO\gemseo\src\gemseo\datasets\dataset.py", line 1053, in <listcomp>
    {k: v.ravel() for k, v in d.items()} for d in list_of_dict_of_arrays
  File "C:\Users\matthias.delozzo\workspace\GEMSEO\gemseo\src\gemseo\datasets\dataset.py", line 1053, in <dictcomp>
    {k: v.ravel() for k, v in d.items()} for d in list_of_dict_of_arrays
AttributeError: 'dict' object has no attribute 'ravel'