docs: def delta_encode(data, axis=-1, out=None):
      """Encode Delta."""
      if isinstance(data, (bytes, bytearray)):
          data = numpy.frombuffer(data, dtype='u1')
          diff = numpy.diff(data, axis=0)
          return numpy.insert(diff, 0, data[0]).tobytes()
  
      dtype = data.dtype
      if dtype.kind == 'f':
          data = data.view('u%i' % dtype.itemsize)
  
      diff = numpy.diff(data, axis=axis)
      key = [slice(None)] * data.ndim
      key[axis] = 0
      diff = numpy.insert(diff, 0, data[tuple(key)], axis=axis)
  
      if dtype.kind == 'f':
          return diff.view(dtype)
      return diff