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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def pretty_relpath(path, start):
    '''
    Returns a relative path, but only if it doesn't start with a non-pretty parent directory ".."
    '''
    relpath = os.path.relpath(path, start)
    if relpath.startswith('..'):
        return path
    return relpath