Saves Config.

def save_config(self, cmd="save config", confirm=True, confirm_response="y"):
        """Saves Config."""
        self.enable()
        if confirm:
            output = self.send_command_timing(command_string=cmd)
            if confirm_response:
                output += self.send_command_timing(confirm_response)
            else:
                # Send enter by default
                output += self.send_command_timing(self.RETURN)
        else:
            # Some devices are slow so match on trailing-prompt if you can
            output = self.send_command(command_string=cmd)
        return output