[BUG][Python] deepObject parameter style creates invalid code on 5.0.1 and raises exception on 5.1.1

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?

Description

when having a spec with deep objects parameter style, the python codegen creates invalid code on generator 5.0.x and fails altogether on generator 5.1.x

on 5.0.x the bad code generated looks like
api_50/api/hosts_api.py:from api_50.model.str_bool_date_datetime_dict_float_int_list_str_none_type import StrBoolDateDatetimeDictFloatIntListStrNoneType

on 5.1.x even considering them triggers

[main] ERROR o.o.codegen.DefaultCodegen - Undefined property/schema for `filter`. Default to type:string.
[main] ERROR o.o.codegen.DefaultCodegen - Undefined property/schema for `filter`. Default to type:string.
Exception in thread "main" java.lang.RuntimeException: Could not process operation:

openapi-generator version

• 5.1.1
• 5.0.1

OpenAPI declaration file content or url

api spec

relevant item is a used

components:
  parameters:
    filter_param:
      in: query
      name: filter
      required: false
      style: deepObject
      explode: true
      schema:
       type: object

Generation Details/ steps to reproduce

• log with 5.0.1
• log with 5.1.1

Related issues/PRs

i haven't found anything quite related

Suggest a fix

my current workaround is to use 5.1.x templates , the 5.0.x codegen and to post-process the generated files dropping the bad lines
it would be nice if there was a configuration option to set a deep_object_hook so users can provide a own serialization/de-serialization for deep_objects

Start with the linked api YAML and generation logs, reproducing the deepObject filter parameter behavior on generator 5.0.1 and 5.1.1. Inspect the Python generator path that produces api_50/api/hosts_api.py. Done means generation completes without the exception and produces valid Python without the invalid model import.