ob key getNode node-value
ob is a class object or an array.
The operator getNode returns the node with the key in ob.
When ob is a class, the node is an array of the format [key attr-list node-list]
When ob is an array, the node is a value of key-value pairs.
/dog [(dog) [[(legs) 4] ] [ ]] [(class) (tree)] dc def
/man [(man) [[(legs) 2] ] [ ]] [(class) (tree)] dc def
/ma [(mammal) [ ] [man dog]] [(class) (tree)] dc def
ma (dog) getNode
[ [1 ] [2 3] [[(dog) 2]]] (dog) getNode ::