extract Sequence as PyType?

[samuelcolvin]

I'd like to do an is_instance check with typing.Sequence, however

let sequence_type: &PyType = sequence_obj.extract();

Is failing with TypeError: '_SpecialGenericAlias' object cannot be converted to 'PyType'.

Is this a fundamental limitation of the python C API, or something that pyo3 could support?

Mostly for my record, here's the failing test from pydantic-core:

def test_is_instance_sequence():
    v = SchemaValidator({'type': 'is-instance', 'cls': typing.Sequence})
    assert v.isinstance_python(1) is False
    assert v.isinstance_python([1]) is True

Fails when creating the SchemaValidator with:

    def test_is_instance_sequence():
>       v = SchemaValidator({'type': 'is-instance', 'cls': typing.Sequence})
E       pydantic_core._pydantic_core.SchemaError: Error building "is-instance" validator:
E         TypeError: '_SpecialGenericAlias' object cannot be converted to 'PyType'

tests/validators/test_is_instance.py:204: SchemaError

[birkenfeld]

OK, I assume sequence_obj is typing.Sequence. This is a case not supported by our current API, but without problems in the C API.

[birkenfeld]

I've opened #2694 to track this.