import time


def ping_with_wait(seconds_to_wait):
	"""
	Wait N seconds, then reply with a message.
	"""
	if not seconds_to_wait:
		raise ValueError("Function argument 'seconds_to_wait' is mandatory and has no default.")
	seconds_to_wait = int(seconds_to_wait)
	if seconds_to_wait < 0:
		raise ValueError("Argument 'seconds_to_wait' cannot be less than 0.")
	print(f"Waiting {seconds_to_wait} seconds before replying...")
	time.sleep(seconds_to_wait)
	print("Pong!")
	return "I have sent a 'pong'; this function is concluded."