Problem when reading the image file.

[YukioOobuchi]

There is currently a known problem with loading image files, such as gif files, when you install nnabla for the first time.
This is due to the upgrade of the Pillow library.

We are currently working on it.

But if you are in a hurry, the workaround is to downgrade Pillow with following command.

pip install pillow \< 8.3.0

after nnabla installed.