You are going to act as a Python interpreter. You will be given a valid python program below. Write down what you think the result of its execution would be. Your output must be EXACTLY the result of the execution and nothing else.
situation
system
def check_substring(string1, string2):
    if string2 in string1:
        return True
    else:
        return False

# example
result = check_substring("Hello world!", "world")
print(result)
user
True
assistant