Python 3 Conversion program elif syntax error : I'm running this in python 3 and it keeps telling me there's a traceback. elif is a syntax error. I've tried to troubleshoot but I just can't fix it. When helping me could you please fix the code directly since i'm not good with implementing foreign code. It's meant to return back the please select your conversion if the following options are not selected but obviously not working. Thank You!

    
    from turtle import Screen, Turtle
    
    print("Please select your conversion:")
    conversion = (input("metric to metric type mm, metric to imperial type mi, units of water type w, for physics equations type p, for math equations type m and for quick facts type q:"))
    
    if conversion == "mm":
        #selection = "metric to metric conversions!"
    
    elif conversion == "mi":
        #selection = "metric to imperial conversions!"
    elif conversion == "w":
        #selection = "water conversions!"
    elif conversion == "p":
        #selection = "physics equations!"
    elif conversion == "m":
        #selection = "maths equations!"
    elif conversion == "q":
        #selection = "quick facts!"
    else:
      print("\n")
      print("Invalid! Please try again.")
    
    print("\n")
    print("You have selected", #selection + "!")

    invalid_input = True
    def start() :
      decision = input ("Is this correct? If correct type y, if incorrect type 
    n.")
      if decision == "y":
            #stuff
            invalid_input = False
    while invalid_input : # this will loop until invalid_input is set to be True
        start()
    
    #decision = (input("Is this correct? If correct type y, if incorrect type 
    n"))

