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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_idx(self):
 """int or str representing index of anchor element in dimension. When the anchor is an operation, like 'top' or 'bottom' """

        anchor = self.anchor
        if anchor in ["top", "bottom"]:
            return anchor
        return self.valid_elements.get_by_id(anchor).index_in_valids