code: @Override
    public void process(Node externsRoot, Node jsRoot) {
      Node externsAndJs = jsRoot.getParent();
      checkState(externsAndJs != null);
      checkState(externsRoot == null || externsAndJs.hasChild(externsRoot));
  
      inferAllScopes(externsAndJs);
    }
docs: Main entry point for type inference when running over the whole tree.
  
  @param externsRoot The root of the externs parse tree.
  @param jsRoot The root of the input parse tree to be checked.