code: protected function parse_callback($conditions, $recursive = true, $check_root = false) {
  		return ($this->result = $this->root->getChildrenByMatch(
  			$conditions,
  			$recursive,
  			$check_root,
  			$this->custom_filter_map
  		));
  	}
docs: Evaluate root node using custom callback
  @param array $conditions {@link parse_conditions()}
  @param bool|int $recursive
  @param bool $check_root
  @return array
  @access private