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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 _get_index(self):
 """ Get the anchor's index. This must return an ``int``. Subclasses may override this method. """

        glyph = self.glyph
        if glyph is None:
            return None
        return glyph.anchors.index(self)