在跟着图像识别的帮助文档时报错：

raceback (most recent call last):
File "D:/BaiduAIstudy/0912/main.py", line 130, in
print_result("./food1.jpg", url)
File "D:/BaiduAIstudy/0912/main.py", line 109, in print_result
'image': base64.b64encode(file_content),
File "D:\python3.9\lib\base64.py", line 58, in b64encode
encoded = binascii.b2a_base64(s, newline=False)
TypeError: a bytes-like object is required, not 'NoneType'

请问该怎么解决？API KEY 以及 Secret KEY都改好了