1.142.3 RootNamespace: overrides for superspaces
- Answer a Set of all the keys in the receiver and its superspaces
- set: key to: newValue ifAbsent: aBlock
- Assign newValue to the variable named as specified by `key'.
This method won't define a new variable; instead if the key
is not found it will search in superspaces and evaluate
aBlock if it is not found. Answer newValue.