Unneccessary ValueError in instancenormalization.py

[frederikfaye]

I'm failing to see the reasoning behind these lines: https://github.com/keras-team/keras-contrib/blob/5ffab172661411218e517a50170bb97760ea567b/keras_contrib/layers/normalization/instancenormalization.py#L80-L81

Say I want to apply an InstanceNormalization layer to tensors all different ranks (e.g. coming from Dense and Conv2D layers), and I always want InstanceNormalization to be applied to the feature axis. If I have data_format == 'channels_last' I think it would make sense that I could simply pass axis=-1 to all my InstanceNormalization layers.

However, because of the above two lines, this doesn't work for rank 1 tensors (coming from e.g. Dense layers).

I deleted the above lines and my solution with axis=-1 for all layers now works.

Shouldn't axis=1 and axis=-1 be perfectly valid values when passing rank 1 tensors?