def encode(message):
    """
    Write a function that takes a message, and encodes in such a 
    way that it swaps case of all letters, replaces all vowels in 
    the message with the letter that appears 2 places ahead of that 
    vowel in the english alphabet. 
    Assume only letters. 
    
    Examples:
    >>> encode('test')
    'TGST'
    >>> encode('This is a message')
    'tHKS KS C MGSSCGG'
    
    Example solution:
    # line 1
    vowels = "aeiouAEIOU"
    # line 2
    vowels_replace = dict([(i, chr(ord(i) + 3)) for i in vowels])
    # line 3
    message = message.swapcase()
    # line 4
    return ''.join([vowels_replace[i] if i in vowels else i for i in message])
    
    """
    # Please print out which line of the above program contains an error. E.g. if the bug is on line 4 then print 4
    # END OF CONTEXT
    print("2")
    # END OF SOLUTION

def check(candidate):

    import io
    from contextlib import redirect_stdout

    f = io.StringIO()
    with redirect_stdout(f):
        candidate([])
    out = f.getvalue().strip('\n')

    assert "2" == out
    for i in range(0, 10):
        if i != 2:
            assert str(i) != out

if __name__ == '__main__':
    check(encode)
