key =  string
value =  int | string | array | object 

array = a sequence of `values`
object = key + value pairs

node = value | array_node | object_node
node_id = int

ops:
 - search(node_id) -> value
 - get_child(node_id, child_id) -> value
 - get_child(node_id, key) -> value
 - get_child_count(node_id) -> int
 - get_key(node_id, child_id) -> key
 - append(node_id, value) -> node_id
 - set(node_id, key, value) -> node_id

impl:
 - stored as an array of `node` indexed by `node_id`
 - search -> O(1) just direct access
 - `array` -> implemented as btree-like structure (values are node_ids)
 - `object` -> implemented as btree-like structure (values are key:node_ids)
 - get_child -> O(log(m)) where `m` is items in that tree, simple access
 - get_key -> same as get child
 - append -> insert into tree
 - set -> insert into tree