add implicit def Key -> (Key, NodeSet())

to fix this problem:
reqT> Submodel(G(2).has())
<console>:24: error: overloaded method value apply with alternatives:
(value: reqt.Model)reqt.Submodel <and>
(kv1: (reqt.Key, reqt.NodeSet),kvs: (reqt.Key,
reqt.NodeSet)*)reqt.Submodel
cannot be applied to (reqt.Key)
Submodel(G(2).has())
^
BUT WHY DID THIS WORK without the new implicit:
reqT> Model(G(1).has())
res14: reqt.Model = Model(Goal("1") has ())
?????