def METHOD_NAME(self, sequence):
    """
    Update the set with the given iterable sequence, then return the index
    of the last element inserted.
    """
    item_index = None
    try:
        for item in sequence:
            item_index = self.add(item)
    except TypeError:
        raise ValueError(
            "Argument needs to be an iterable, got {}".format(type(sequence))
        )
    return item_index