python client produces invalid pattern regex with metacharacters - eg \d

Description

Building a swagger python client with a pattern, in this case P\d+' results in a raw string that's escaped: r'P\\d+' which matches something like P\3 but not valid input like P3.

Swagger-codegen version

2.4.6
This used to produce valid regex's.

Swagger declaration file content or url

Command line used for generation

docker run --rm \
    -v $PWD/generated_$1:/swagger-api/out \
    -v $PWD:/swagger-api/yamls \
    -it swaggerapi/swagger-codegen-cli:2.4.6 generate \
    -i /swagger-api/yamls/swagger.yaml \
    -l python \
    -o /swagger-api/out \
    --config /swagger-api/yamls/config.json

Steps to reproduce

generate python client.
Then try to use the client the resulting regex will always fail with valid content

        if 'fooid' in params and not re.search(r'FOO\\d+', params['fooid']):  # noqa: E501

Related issues/PRs

Suggest a fix/enhancement

removing the r in the template fixes this issue which was the behavior of some earlier versions.