Function unpack_bitstream_numpy 

pub(crate) fn unpack_bitstream_numpy<'py>(
    py: Python<'py>,
    packed: PyReadonlyArray1<'py, u64>,
    original_length: usize,
) -> PyResult<Bound<'py, PyArray1<u8>>>

Unpack a numpy uint64 array back to a numpy uint8 array.