[Config] Allow to get parent of BaseNode

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no (improvement)
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        | 

Like an ArrayNode have method `getChildren`, I might to be good idea for having method `getParent` of all nodes.