Looks like `spdxId` does not have cardinality information

[bact]

When use Element.spdxId in Python code, the IDE/linter expects spdxId to be either str or None.

But as cardinality of spdxId (in Element) is 1..1, it should not be the case. It should expect only str.

Not sure if it is anything to do with the fact that we treat spdxId as an alias of _id/@id (so the generation code may differ from other properties).

[bact]

Work around on consumer side is do None check or cast. To confirm with linter that it can't be None.

[bact]

Investigate this a bit in shacl2code (where the binding actually get generated), looks like there is no clean way to do this as shacl2code is meant to be for general purpose, not SPDX 3 specific.

In terms of actual data, the spdxId presence is guaranteed by encode(). So we are good here.

The only concern is about the ergonomic during development time (static analysis), but I guess we can live with it.

(Note: The JSON Schema generator did actually check for the _id (https://github.com/JPEWdev/shacl2code/blob/f5747f446e2ef1b107e928ef3ef2a5b309bcf47e/src/shacl2code/lang/templates/jsonschema.j2#L104-L106), but it only deal with validation, not construction -- similar to encode() above)