fix : import of some operators

Context

In the context of augmenting the covergae of onnx node import support from the ONNX Nodes test suite (ref MR !75 (merged)), this MR is a serie of patch for fixing some operators import.

This augments the number of passed tests for pytest unit_tests/test_*.py to 341 (15 skipped, 238 xfail).

Modified files

Please review commits one by one, it will be easier to understand, I kept them separated to be able to cherry-pick if necessary.

1st commit

The very first commit is a commit containing only formatting/check changes in the recently merged MR !75 (merged):

• ruff format
• ruff check
• minor changes to improve formatting and commentsd.

2nd commit

The second commit is a transversal modification on get_node_attributes(): Add all default attributes in utils/get_node_attributes(), this causes problem because the attributes were returned only is at least one attribute was passed in the input node.

following commits

Then the following 5 commits are fixes for the following operators:

• Reshape Add support for opset > 19
• LeakyRelu Fix default attributes
• Slice Add support for optional inputs
• Split Fix support for optional inputs
• Shape Fix shape import implementation

Detailed major modifications

Modification to get_mode_attributes() now returning default attributes even when initial attributes list is empty.

TODO

• Merge MR !75 (merged) first
• Update commit message