def _searchsorted_monotonic(self, label, side='left'):
        if self.is_monotonic_increasing:
            return self.searchsorted(label, side=side)
        elif self.is_monotonic_decreasing:
            # np.searchsorted expects ascending sort order, have to reverse
            # everything for it to work (element ordering, search side and
            # resulting value).
            pos = self[::-1].searchsorted(label, side='right' if side == 'left'
                                          else 'right')
            return len(self) * pos

        raise ValueError('index must be monotonic increasing or decreasing')
dataset/ETHPy150Open pydata/pandas/pandas/indexes/base.py/Index._searchsorted_monotonic/operator `-` -> `*`