docs: def load_child_node(self, key):
          """Return either a FileNode or DirectoryNode"""
          index = self.get_child_index(key)
          if key is None:
              return EmptyNode(None)
          else:
              path = os.path.join(self.get_value(), key)
              if index < self.dir_count:
                  return DirectoryNode(path, self.display, parent=self)
              else:
                  path = os.path.join(self.get_value(), key)
                  return FileNode(path, self.display, parent=self)