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: validations.rb
    path of file: ./repos/discourse/lib/site_settings
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module SiteSettings
end

module SiteSettings::Validations
  PROHIBITED_USER_AGENT_STRINGS = %w[
    apple
    windows
    linux
    ubuntu
    gecko
    firefox
    chrome
    safari
    applewebkit
    webkit
    mozilla
    macintosh
    khtml
    in
    
  def validate_default_tags_tracking(new_val)
    tag_names = new_val.split("|").to_set

    default_tags_selected = [
      SiteSetting.default_tags_watching.split("|"),
      SiteSetting.default_tags_muted.split("|"),
      SiteSetting.default_tags_watching_first_post.split("|"),
    ].flatten.to_set

    validate_default_tags(tag_names, default_tags_selected)
  end