[BUG] Python Client Code Regex `\n` Handle Problem

[wy193777]

Bug Report Checklist

• [x] Have you provided a full/minimal spec to reproduce the issue?
• [ ] Have you validated the input using an OpenAPI validator (example)?
• [x] What's the version of OpenAPI Generator used?
• [x] Have you search for related issues/PRs?
• [x] What's the actual output vs expected output?
• [ ] [Optional] Bounty to sponsor the fix (example)

Description

When try to generate python client from this Swagger file, it cannot handle parameter regex validation with \n.

openapi-generator version

4.0.0-beta3

OpenAPI declaration file content or url

https://gist.githubusercontent.com/wy193777/e2da6ad64259cc1ad6a672aae55b1d23/raw/f0ae7cf8bb36458298fd7e0e2ed1b099072d40d3/swagger.json

Command line used for generation

openapi-generator generate -i https://gist.githubusercontent.com/wy193777/e2da6ad64259cc1ad6a672aae55b1d23/raw/f0ae7cf8bb36458298fd7e0e2ed1b099072d40d3/swagger.json -g python -o code\jama-client --skip-validate-spec

Steps to reproduce

Generate client, then run tests.

Related issues/PRs

Suggest a fix

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