def get_index_from_base_index(self, base_index):
        """Get index into this array's data given the index into the base array
        """
        r = self.rawdata
        try:
            index = r.get_reverse_index(base_index)
        except IndexError:
            raise IndexError("index %d not in this segment" % base_index)
        if index < 0:
            raise IndexError("index %d not in this segment" % base_index)
        return int(index)
Get index into this array's data given the index into the base array