You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: ast.rb
    path of file: ./repos/danbooru/app/logical/post_query
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

# A PostQuery::AST is an abst
    
      def parents
        parents = []

        node = self
        until node.parent.nil?
          parents << node.parent
          node = node.parent
        end