def sym_pairwise(arg1, arg2):
    """Calculates the symmetric difference of two
    sets.

    Arguments:
        arg1 -- the first set
        arg2 -- the second set

    Returns: the symmetric difference of two sets
    """
    result = []

    # Add each element in arg1 to result as long
    # as the element is not in arg2 and not
    # already in result.
    for element in arg1:
        if element not in arg2 and element not in result:
            result.append(element)

    # Add each element in arg2 to result as long
    # as the element is not in arg1 and not
    # already in result.
    for element in arg2:
        if element not in arg1 and element not in result:
            result.append(element)

    return result