I figure out you want
listb.pop is a valid python expression which results in a reference to the
pop method, however doesn't really call that method. You require to include the open and close parentheses to call the method.
 instead of
() at the time attempting to call
Seems like you typed brackets instead of parenthesis by mistake.
You are attempting to access pop as in case was a list or a tupple, however pop is not. It's a method.
instead of writing
This error arises at the time you don't use brackets with
pop operation. Write the code in this manner.
or You can attempt this code
featIndex = featLabels.index(firstStr)