[BUG] Schema $ref with same name is not producing models properly

Created by: vinodchitrali

Bug Report Checklist

Have you provided a full/minimal spec to reproduce the issue?
Have you validated the input using an OpenAPI validator (example)?
What's the version of OpenAPI Generator used?
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What's the actual output vs expected output?
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Description

My schema definition are spread across multiple files and they are cross reference(using $ref). In these files there is one schema with same name. I have 5 such instances

When i run code generator, Only 2 models are produced. Rest are ignored. Some of the $ref are pointing to wrong model.

Here is example given below

openapi-generator version

4.0.0-beta

OpenAPI declaration file content or url

https://gist.github.com/vinodchitrali/c5cd3be1c8d6fb0d2fb6bcf6a530ad94

Command line used for generation

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar  generate -i ./api/openapi.yaml   -g python -o /tmp/python/ --api-package api --model-package model --additional-properties projectName=python

Steps to reproduce

Copy the Yaml files from https://gist.github.com/vinodchitrali/c5cd3be1c8d6fb0d2fb6bcf6a530ad94
java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -i ./api/openapi.yaml -g python -o /tmp/python/ --api-package api --model-package model --additional-properties projectName=python
Check files generated in /tmp/python/openapi_client/model/