how can I unpack non_iterables NonType object in my script

I have tried using all the iterating methods but still getting the same error, I have tried using itertools.zip_longest but still giving me the same error

def find_occurrences(content_string):
    start_indices = []
    end_indices = []
    for i in range(len(content_string)):
        if content_string.startswith("https://www.nytimes.com/2022", i):
            start_indices.append(i)
        if content_string.startswith(".html", i):
            end_indices.append(i+5)

    #print(start_indices)
    #print(end_indices)

find_occurrences(content_string)   


def get_all_urls(start_indices, end_indices, content_string ):
    
    url_list = []
    for (i) in range (len(start_indices)):
        url_list.append(content_string [start_indices[i]:end_indices[i]])
    return url_list
    

content_string = get_content_string("https://www.nytimes.com/section/technology")
start_indices, end_indices = find_occurrences(content_string)
url_list = get_all_urls(start_indices, end_indices, content_string)

this is the error I amm getting

Exception has occurred: TypeError
cannot unpack non-iterable NoneType object
  File "C:\Users\HP\OneDrive\Desktop\Newspaper Aggregator\projects\news_extract.py", line 52, in <module>
    start_indices, end_indices = find_occurrences(content_string)