Fixes serialization of array items in model_to_dict [python]

[spacether]

Fixes serialization of array items in model_to_dict [python]
If merged, this will resolve #8770

Tests of serialization and deserialization have been added in:

• test_get_inline_additional_properties_ref_payload
• test_get_inline_additional_properties_payload

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[jsok]

This fails to handle the case where v is a dict, i.e. a free-form object.

e.g. a spec like:

        "type": "array",
        "items": {
          "type": "object",
          "additionalProperties": true
        },

[spacether]

That could be a bug related to inline schema handling.
Is there a model made and used for that schema?
If so, we handle it with line 1225
Can you want to post an issue describing the problem that you've found? Or a PR fixing it?

[jsok]

Good points, I'm not sure if the codegen is wrong or if the model_to_dict is just missing the specific case.

The generated client code I'm experiencing this issue with is: https://github.com/sajari/sdk-python/blob/6bf9c20e4a2639eaf9774d1770b6a7ac39ed33c0/sajari_client/model/batch_upsert_records_request.py#L130-L131

e.g. when I attempt to serialise my request like:

        request = BatchUpsertRecordsRequest(
            pipeline=BatchUpsertRecordsRequestPipeline(name="app", version="1"),
            records=BatchUpsertRecordsRequestRecords([{"foo": "bar"}]),
            variables={},
        )
        model_to_dict(request, serialize=True)

it fails with:

Traceback (most recent call last):
  File "/Users/jsok/dev/github.com/sajari/sdk-python/test/test_reproduction.py", line 83, in test_request_serialisation
    print(model_to_dict(request, serialize=True))
  File "/Users/jsok/dev/github.com/sajari/sdk-python/sajari_client/model_utils.py", line 1693, in model_to_dict
    res.append(model_to_dict(v, serialize=serialize))
  File "/Users/jsok/dev/github.com/sajari/sdk-python/sajari_client/model_utils.py", line 1665, in model_to_dict
    if model_instance._composed_schemas:
AttributeError: 'dict' object has no attribute '_composed_schemas'

Happy to contribute a PR that makes the fix in the model_to_dict method if that's the right place for it.