def shift_128(input: np.ndarray, quant_dtype: np.dtype) -> np.ndarray:
        """
        shift const input according to zero point shift and dtype change:
            int8: -128 -> 0, int8 -> uint8
            uint8: 128 -> 0, uint8 -> int8
        """
        shifted_input: np.ndarray
        if quant_dtype == np.int8:
            shifted_input = np.uint8(np.int16(input) + 128)
        else:
            shifted_input = np.int8(np.int16(input) - 128)
        return shifted_input

        shift const input according to zero point shift and dtype change:
            int8: -128 -> 0, int8 -> uint8
            uint8: 128 -> 0, uint8 -> int8
        
coremltools/converters/mil/mil/passes/tests/test_quantization_passes.py