Openflow-Action list needs a key?

I am using `pyang` to validate a yang module which I am basing off of openflow. In the process of building it out, I am validating my yang through pyang and I am noticing this error:

$ pyang my.yang
openflow-instruction@2013-07-31.yang:21: error: the list at "openflow-instruction@2013-07-31.yang:21 (at openflow-action@2015-02-03.yang:32)" needs at least one key because it is used as config

When looking at the source code for openflow-action I see:

 grouping actions-grouping {
   list action {
      uses action-grouping;
      leaf experimenter-id {
        type oft:experimenter-id;
     }
}

So it is missing a `key`. I can't tell if this is a bug with openflow-action or if pyang is running in some ultra strict mode, but does anyone have insight on this?