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: connection_methods.rb
    path of file: ./repos/activerecord-jdbc-adapter/lib/arjdbc/mysql
    
    the code of the file until where you have to start completion: # frozen_string_literal: true
ArJdbc::ConnectionMethods.module_eval do
  def mysql_connection(config)
    config = config.deep_dup
    # NOTE: this isn't "really" necessary but Rails (in tests) assumes being able to :
    #   ActiveRecord::Base.mysql2_connection ActiveRecord::Base.configurations['arunit'].merge(database: ...)
    config = symbolize_keys_if_necessary(config)

    config[:adapter_spec] ||= ::ArJdbc::MySQL
    config[:adapter_class] = ActiveRecord::ConnectionAdapters::Mysql2Adapter unless config.key?(:adapter_class)

    return jndi_connection(config) if jndi_config?(config)

    driver = config[:driver]
    mysql_driver = driver.nil? || driver.to_s.start_with?('com.mysql.')
    mariadb_driver = ! mysql_driver && driver.to_s.start_with?('org.mariadb.')

    begin
      require 'jdbc/mysql'
      ::Jdbc::MySQL.load_driver(:require) if defined?(::Jdbc::MySQL.load_driver)
    rescue LoadError # assuming driver.jar is on the class-path
    end if mysql_driver

    if driver.nil?
      config[:driver] ||=
        defined?(::Jdbc::MySQL.driver_name) ? ::Jdbc::MySQL.drive
    
  def convert_mysql_encoding(encoding) # to charset-name (characterEncoding=...)
    ( @@mysql_encodings ||= {
      "big5" => "Big5",
      "dec8" => nil,
      #"cp850" => "Cp850",
      "hp8" => nil,
      #"koi8r" => "KOI8-R",
      "latin1" => "Cp1252",
      "latin2" => "ISO8859_2",
      "swe7" => nil,
      "ascii" => "US-ASCII",
      "ujis" => "EUC_JP",
      "sjis" => "SJIS",
      "hebrew" => "ISO8859_8",
      "tis620" => "TIS620",
      "euckr" => "EUC_KR",
      #"koi8u" => "KOI8-R",
      "gb2312" => "EUC_CN",
      "greek" => "ISO8859_7",
      "cp1250" => "Cp1250",
      "gbk" => "GBK",
      #"latin5" => "ISO-8859-9",
      "armscii8" => nil,
      "ucs2" => "UnicodeBig",
      "cp866" => "Cp866",
      "keybcs2" => nil,
      "macce" => "MacCentralEurope",
      "macroman" => "MacRoman",
      #"cp852" => "CP852",
      #"latin7" => "ISO-8859-13",
      "cp1251" => "Cp1251",
      "cp1256" => "Cp1256",
      "cp1257" => "Cp1257",
      "binary" => false,
      "geostd8" => nil,
      "cp932" => "Cp932",
      #"eucjpms" => "eucJP-ms"
      "utf8" => "UTF-8",
      "utf8mb4" => false,
      "utf16" => false,
      "utf32" => false,
    } )[ encoding ]
  end