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: code_search.rb
    path of file: ./repos/ruby/lib/syntax_suggest
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module SyntaxSuggest
  # Searches code for a syntax error
  #
  # There are three main phases in 
    
    def expand_existing
      block = frontier.pop
      return unless block

      record(block: block, name: "before-expand")

      block = @block_expand.call(block)
      push(block, name: "expand")
    end