[RUBY] Bug generated code does not have inheritance

Description

I am trying to generate ruby code for the .json file provided below. It generates fine, but the code that comes out of it does not have any inheritance, while in the code it uses super, so it should clearly have that. When I try to generate the c# code for it, it does have the expected (not sure if it's correct yet) inheritance. Examples

[DataContract]
        public partial class AuthenticationCommand : Command,  IEquatable<AuthenticationCommand>, IValidatableObject

class AuthenticationCommand
    attr_accessor :action_uid

    attr_accessor :pwd

    attr_accessor :user_name

    .....

    def initialize(attributes = {})
      # call parent's initialize
      super(attributes)

Swagger-codegen version

wget https://repo1.maven.org/maven2/io/swagger/codegen/v3/swagger-codegen-cli/3.0.52/swagger-codegen-cli-3.0.52.jar -O swagger-codegen-cli.jar

3.0.52

Swagger declaration file content or url

https://gist.github.com/Ruubb/0724a4d471f4363ebedde7ff6006fce9

Command line used for generation

java -jar swagger-codegen-cli.jar generate -i openapi_clean.json -l ruby -o /path/

Steps to reproduce

1. Download right swagger version
2. Download json file
3. Run the command provided above
4. Look at the generated Ruby code

Related issues/PRs

N/A

Suggest a fix/enhancement

N/A

Start by reproducing the Ruby generation with swagger-codegen-cli 3.0.52, the provided command, and the linked OpenAPI JSON. Compare AuthenticationCommand and its super call with the generated C# inheritance, then verify that the Ruby output represents the expected inheritance consistently.