$ gem install numo-narray
ERROR: Error installing numo-narray:
The last version of numo-narray (>= 0) to support your Ruby & RubyGems was 0.9.0.4. Try installing it with `gem install numo-narray -v 0.9.0.4`
numo-narray requires Ruby version ~> 2.2. The current ruby version is 3.0.0.dev.