Fix attributes dictionary handling in show_graphview.py

Context

aidge_core.Tensor objects found in nodes attributes dictionaries were not handled correctly during JSON description generation from the graph view, leading the script to fail.

Related issue: #264 (moved)

This MR addresses the issue by introducing an adapted serialization approach to aidge_core.Tensor objects. In addition, the json.dump function now uses the default=str option, which resolves most serialization issues encountered with custom types.

Modified files

• aidge_core/show_graphview.py, fix in _retrieve_operator_attrs() function;
• aidge_core/unit_tests/test_show_graphview.py, adaption of unittest so it is coherent with new serialization approach.

Detailed major modifications

aidge_core/show_graphview.py

1. In _retrieve_operator_attrs() function:

• Added serialization for aidge_core.Tensor;
• Removed serialization relying on the node's attribute object name. It is no longer needed, since default=str option is enabled in json.dump() function, which is a more generic approach.

2. In _create_dict() function:

• Standardization: updated the serialization of Producers, which are also aidge_core.Tensor objects, to align with the newly proposed approach.

3. In _create_dict() and _write_dict_json() functions:

• Added the default=str option to the json.dump() function, which provides a fallback function for objects that aren’t natively serializable by JSON.

aidge_core/unit_tests/test_show_graphview.py

• Added a condition to test JSON description files that have been serialized using the new approach.