sequence item 0: expected str instance, NoneType found

This error occurs when you try to use a variable that has a value of None in a context where a string is expected.

For example, if you have a list that contains a None value and you try to access the first item in the list as a string, you will get this error:

my_list = [None, "hello", "world"]
print(my_list[0] + "foo")

Output:
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

To fix this error, you need to make sure that the variable you are trying to use is not None before using it in a string context. One way to do this is to use an if statement:

my_list = [None, "hello", "world"]
if my_list[0] is not None:
print(my_list[0] + "foo")

Output:
(nothing is printed, since the first item in the list is None)