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: pop3_polling_enabled_setting_validator.rb
    path of file: ./repos/discourse/lib/validators
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

require "net/pop"

class POP3PollingEnabledSettingValidator
  def
    
  def valid_value?(val)
    # only validate when enabling polling
    return true if val == "f"
    # ensure we can authenticate
    SiteSetting.pop3_polling_host.present? && SiteSetting.pop3_polling_username.present? &&
      SiteSetting.pop3_polling_password.present? && authentication_works?
  end