How to check if a random mixed case word is in a string

I am trying to check to see if there is the word robot in a line. (I'm learning python. Still very new to it.) If the word 'robot' is in a line it prints something out. Same with 'ROBOT'. However, I need to know how to output when robot is in the line but in a randomly mixed case, eg rObOt. Is this possible? It seems like I would need to write out every combination. I'm using Python 3. Thanks :).

if ' robot ' in line:
  print("There is a small robot in the line.")
elif ' ROBOT ' in line:
  print("There is a big robot in the line.")
elif 'rOBOt' in line:
  print("There is a medium sized robot in the line.")
else:
  print("No robots here.")

Hope the code below can help you.

line = "Hello robot RoBot ROBOT"

l = line.split(" ")

exist = False

for word in l:
    if word.upper() == "ROBOT":

        exist = True

        if word.isupper():
            print("There is a big robot in the line.")
        elif word.islower():
            print("There is a small robot in the line.")
        else:
            print("There is a medium sized robot in the line.")

if not exist:
    print("No robots here.")