code: public static SystemInputDef getRequestInputModel( InputStream api, ModelOptions options)
      {
      try( OpenApiReader reader = new OpenApiReader( api))
        {
        return TcasesOpenApi.getRequestInputModel( reader.read(), options);
        }
      }
docs: Returns a {@link SystemInputDef system input definition} for the API requests defined by the given
  OpenAPI specification. Returns null if the given spec defines no API requests to model.