AttributeError: 'NoneType' object has no attribute 'find_all'

This error occurs when you try to call the method `find_all()` on a variable that is None. The `find_all()` method is a function of the BeautifulSoup object in Python, which is used to parse HTML or XML documents.

Here is an example of how this error might occur:

import requests
from bs4 import BeautifulSoup

# make a request to a webpage
response = requests.get("https://www.example.com")

# parse the HTML content of the webpage using BeautifulSoup
soup = BeautifulSoup(response.content, "html.parser")

# find all the links on the webpage
links = soup.find_all("a")

# print the links
for link in links:
    print(link.get("href"))

If the `response.content` is None or there is some other issue with the request, then `soup` will be None and calling `find_all()` on it will result in the 'NoneType' object has no attribute 'find_all' error.

To avoid this error, you should check that the object you are calling the method on is not None before calling the method.

Here is an example of how you could modify the code above to avoid this error:

import requests
from bs4 import BeautifulSoup

# make a request to a webpage
response = requests.get("https://www.example.com")

# check that the response was successful
if response.status_code == 200:

    # parse the HTML content of the webpage using BeautifulSoup
    soup = BeautifulSoup(response.content, "html.parser")

    # find all the links on the webpage
    if soup is not None:
        links = soup.find_all("a")

        # print the links
        for link in links:
            print(link.get("href"))

    else:
        print("Error parsing HTML content")
else:
    print("Error: could not retrieve webpage")