python 爬取头条街拍是 'NoneType' object has no attribute 'get'

import requests
from urllib.parse import urlencode
from requests import codes
import os
from hashlib import md5
from multiprocessing.pool import Pool
import re

import codecs

def get_page(offset):
    params = {
        'aid': '24',
        'offset': offset,
        'format': 'json',
        #'keyword': '街拍',
        'autoload': 'true',
        'count': '20',
        'cur_tab': '1',
        'from': 'search_tab',
        'pd': 'synthesis'
    }
    base_url = 'https://www.toutiao.com/api/search/content/?keyword=%E8%A1%97%E6%8B%8D'
    url = base_url + urlencode(params)
    try:
        resp = requests.get(url)
        print(url)
        if 200  == resp.status_code:
            print(resp.json())
            return resp.json()
    except requests.ConnectionError:
        return None


def get_images(json):
    if json.get('data'):
        data = json.get('data')
        for item in data:
            if item.get('cell_type') is not None:
                continue
            title = item.get('title')
            images = item.get('image_list')
            for image in images:
                origin_image = re.sub("list", "origin", image.get('url'))
                yield {
                    'image':  origin_image,
                    # 'iamge': image.get('url'),
                    'title': title
                }

print('succ')

def save_image(item):
    img_path = 'img' + os.path.sep + item.get('title')
    print('succ2')
    if not os.path.exists(img_path):
        os.makedirs(img_path)
    try:
        resp = requests.get(item.get('image'))
        if codes.ok == resp.status_code:
            file_path = img_path + os.path.sep + '{file_name}.{file_suffix}'.format(
                file_name=md5(resp.content).hexdigest(),
                file_suffix='jpg')
            if not os.path.exists(file_path):
                print('succ3')
                with open(file_path, 'wb') as f:
                    f.write(resp.content)
                print('Downloaded image path is %s' % file_path)
                print('succ4')
            else:
                print('Already Downloaded', file_path)
    except requests.ConnectionError:
        print('Failed to Save Image，item %s' % item)


def main(offset):
    json = get_page(offset)
    for item in get_images(json):
        print(item)
        save_image(item)


GROUP_START = 0
GROUP_END = 7

if __name__ == '__main__':
    pool = Pool()
    groups = ([x * 20 for x in range(GROUP_START, GROUP_END + 1)])
    pool.map(main, groups)
    pool.close()
    pool.join()

运行的结果是

Traceback (most recent call last):
  File "d:/pyhton/.idea/inspectionProfiles/学习/jiepai.py", line 89, in 
    pool.map(main, groups)
  File "D:\Anaconda3\lib\multiprocessing\pool.py", line 290, in map
    return self._map_async(func, iterable, mapstar, chunksize).get()
  File "D:\Anaconda3\lib\multiprocessing\pool.py", line 683, in get
    raise self._value
AttributeError: 'NoneType' object has no attribute 'get'
succ
succ
succ
succ