Python relies on indentation to demarcate blocks of code, where other languages wrap them in curly braces
Notice how inside your function definition, your first
for is indented a certain amount but your
return as the final line of the function does not have the same amount of indentation. This is your error.
Python requires that you be consistent. To assist with this, you might consider adhering to PEP 8; specifically, indenting by 4 spaces rather than using a tab. (One is subject to interpretation, one is not; spaces are broadly preferable, in my opinion.)
@thepitycoder Many thanks. Really appreciate it.