def sum(self,a=None,b=None,c=None): ### using none we can types nothing in the input if not needed ...

print(calc.add(5)) # Output: 5 (only a is used) print(calc.add(5, 10)) # Output: 15 (a and b are used) print(calc.add(5, 10, 15)) # Output: 30 (a, b, and c are used) ...