timedelta object cannot be interpreted as integer

[DeaD_EyE]

To check if something is in a valid range, you could do following:

minimum_value <= current_value <= maximum_value

All three values should be the same data type.
In your example self.validity should be a timedelta object.

This should work:

                elif self.certification_status == "Fit" and timedelta(days=730) <= self.validity <= timedelta(days=732)):
                    return "Normal"

A example with ip addresses:

from ipaddress import ip_address


def ip_is_in_range(ip, start, end):
    start = ip_address(start)
    end = ip_address(end)
    ip = ip_address(ip)
    return start <= ip <= end

What you've tried with the range object, works for integers.

my_range = range(16, 31, 2)
18 in my_range
17 in my_range
...

# And you can use the range object again and again.
for i in my_range:
    for j in my_range:
        print(i, j)