How do I complete this project?

def encode(message, shift):
	message = message.lower()
	secret = ""
	for c in message:
		if c in "abcdefghijklmnopqrstuvwxyz":
			num = ord(c)
			num += shift
			if num > ord("z"):       
				num -= 26
			elif num < ord("a"):
				num += 26
			secret = secret + chr(num)
		else:
		  secret = secret + c
	return secret
  # this line does nothing. Remove it when you complete the method.

def decode(message, shift):
  
  pass  # this line does nothing. Remove it when you complete the method.

def main():
  msg = input("Your message to encode? ")
  if len(msg) > 0:
	  secret = encrypt(msg)
	  print("The encoded message is:", secret)
  else:
	secret = input("Your message to decode? ")
	if len(secret) > 0:
		msg = decrypt(secret)
		print("The decoded message is:", msg)

  # this line does nothing. Remove it when you complete the method.
  
---"I do not know how to make decode line"---


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###                Do not modify anything below here                 ###
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if __name__ == '__main__':
  main()