code: public function deleteNode(/*# string */ $nodeName)
      {
          if ('' === $nodeName) {
              $this->tree = [];
          } else {
              $current = &$this->getNode($nodeName);
              if (null !== $current) {
                  $split = explode($this->splitter, $nodeName);
                  $name  = array_pop($split);
                  $upper = &$this->getNode(join($this->splitter, $split));
                  unset($upper[$name]);
              }
          }
          return $this;
      }
docs: {@inheritDoc}