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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 anchor(self):
 """int or str indicating element under which to insert this subtotal. An int anchor is the id of the dimension element (category or subvariable) under which to place this subtotal. The return value can also be one of 'top' or 'bottom'. The return value defaults to 'bottom' for an anchor referring to an element that is no longer present in the dimension or an element that represents missing data. """

        anchor = self._subtotal_dict["anchor"]
        try:
            anchor = int(anchor)
            if anchor not in self.valid_elements.element_ids:
                return "bottom"
            return anchor
        except (TypeError, ValueError):
            return anchor.lower()