find the biggest ball - detect object

Question

i am a newby in python and i am researching about detect object. I'm looking for the biggest ball. I have no idea how to make it work. Can anybody give me some pointers? Here is what I have so far. my code: (from: "https://youtu.be/Vg9rrOFmwHo")

import cv2
import serial
from time import sleep


classNames = []
classFile = "/home/pi/Desktop/Object_Detection_Files/coco.names"
with open(classFile,"rt") as f:
    classNames = f.read().rstrip("\n").split("\n")

configPath = "/home/pi/Desktop/Object_Detection_Files/ssd_mobilenet.pbtxt"
weightsPath = "/home/pi/Desktop/Object_Detection_Files/frozen_inference_graph.pb"

net = cv2.dnn_DetectionModel(weightsPath,configPath)
net.setInputSize(320,320) 
net.setInputScale(1/ 127.5)
net.setInputMean((127.5, 127.5, 127.5))
net.setInputSwapRB(True)


def getObjects(img, thres, nms, draw=True, objects=[]):
    classIds, confs, bbox = net.detect(img,confThreshold=thres,nmsThreshold=nms)
    if len(objects) == 0: objects = classNames
    objectInfo =[]
    if len(classIds) != 0:
        for classId, confidence,box in zip(classIds.flatten(),confs.flatten(),bbox):
            className = classNames[classId - 1]
            if className in objects:
                objectInfo.append([box,className])
                if (draw):
                    cv2.rectangle(img,box,color=(0,255,0),thickness=2)
                    cv2.putText(img,'sports ball',(box[0]+10,box[1]+30),
                    cv2.FONT_HERSHEY_COMPLEX,1,(0,255,0),2)
                    x= int(box[0]+box[2]/2)
                    y= int(box[1]+box[3]/2)
                    cv2.circle(img, (x, y), 5, (0,255,0), 1)     
                  
    return img,objectInfo


if __name__ == "__main__":

    cap = cv2.VideoCapture(0)
    cap.set(3,640)
    cap.set(4,480)

    while True:
        success, img = cap.read()
        height, width, _ = img.shape
        result, objectInfo = getObjects(img,0.29,0.2, objects=['sports ball'] )
        #print(objectInfo)
        cv2.imshow("Output",img)
        cv2.waitKey(1)