Understand it.
Then build it.

hello_node.py · complete node pattern

import rclpy
from rclpy.node import Node

class HelloNode(Node):
    def __init__(self):
        super().__init__('hello_node')
        self.get_logger().info('hello_node is alive')

def main():
    rclpy.init()
    node = HelloNode()
    try:
        rclpy.spin(node)
    finally:
        node.destroy_node()
        rclpy.shutdown()