Integrate chirpstack and paho mqtt

Can anybody help to integrate chirptsack command with paho mqtt.
Thank you

from paho.mqtt import client as mqtt_client
import threading
import base64
import random

broker = None
port = 1883
client = None
topic_up = “application/1/device/+/event/up”
client_id = f’python-mqtt-{random.randint(0, 100)}’

def connect_mqtt() → mqtt_client:
“”“Connects MQTT client to broker”""
def on_connect(client, userdata, flags, rc):
if rc == 0:
print(“Connected to MQTT Broker!”)
print(“Failed to connect, return code %d”, rc)

client = mqtt_client.Client(client_id)
client.on_connect = on_connect
client.connect(broker, port)
return client

def subscribe(client: mqtt_client):
“”“MQTT subscribe function which the MQTT client listens on”""
def on_message(client, userdata, msg):

    decoded_payload = str(msg.payload.decode("utf-8"))
    frame = json.loads(decoded_payload)

    deviceEUI = frame['devEUI']
    frameCounter = frame['fCnt']
    SNR = frame["rxInfo"][0]['loRaSNR']
    RSSI = frame["rxInfo"][0]['rssi']
    datarate = frame["txInfo"]['dr']
    frequency = frame["txInfo"]['frequency'] / 1000000

    payload = base64.b64decode(frame['data']).hex()

client.on_message = on_message

def publish(client: mqtt_client, device_eui):
“”“Downlink new settings to sensor via ChirpStack”""
payload = “AA BB FF”
topic_down = f"application/1/device/{device_eui}/command/down"

frame = {
    "confirmed": True,
    "fPort": 2,
    "data": base64.b64encode(bytes.fromhex(payload)).decode()

data = json.dumps(frame)
client.publish(topic_down, data)

def start_mqtt_client(hostname):
“”“Starts a MQTT client, which subscribes to a topic in a loop”""
global client
global broker
broker = hostname
client = connect_mqtt()

Thanks for the reply
Im little bit new can you please help to figure out what this code does.