Jenkins Node Image at Kubernetes Plugin
Have a look at the documentation presented here:

https://github.com/jenkinsci/kubernetes-plugin

You need to specify a Kubernetes pod in your pipeline. An example of your use case would look similar to this for a single python container. You'll notice that containers: [] expects an array so you can include additional containers.

def label = "mypod-${UUID.randomUUID().toString()}"

podTemplate(label: label, containers: [
    containerTemplate(name: 'python', image: 'python:3.7-alpine', ttyEnabled: true, command: 'cat'),
]) {
    node(label) {
        stage('Get a Python project') {
            git 'https://github.com/oğuz/project.git'
            container('python') {
                stage('Test a Python project') {
                    sh "python -m -v py.test TEST_FILE.py "
                }
            }
        }
    }
}