Perform a DUP operation on the stack.

def dup(self, position: int) -> None:
        """
        Perform a DUP operation on the stack.
        """
        idx = -1 * position
        try:
            self.push(self.values[idx])
        except IndexError:
            raise InsufficientStack("Insufficient stack items for DUP{0}".format(position))