[BUG] [Python] model.mustache import error

Created by: JoeCqupt

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Have you provided a full/minimal spec to reproduce the issue?
Have you validated the input using an OpenAPI validator (example)?
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Description

when i extend PythonClientCodegen to make myown python code generator; i set modelPackage and etc.....

modelPackage = packageName + ".common.model";

finally the client code not can not run , because the model.mustache import error

from {{packageName}}.model_utils import (  # noqa: F401
    ApiTypeError,
    ModelComposed,
    ModelNormal,
    ModelSimple,
    cached_property,
    change_keys_js_to_python,
    convert_js_args_to_python_args,
    date,
    datetime,
    file_type,
    none_type,
    validate_get_composed_info,
)
from ..model_utils import OpenApiModel

the OpenApiModel use relative path

openapi-generator version

master branch

OpenAPI declaration file content or url

Generation Details

Steps to reproduce

Related issues/PRs

i will make a pr to fix it latter #10988

Suggest a fix

i will make a pr to fix it latter #10988