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: common.rb
    path of file: ./repos/ferrocarril/mruby/src/extn/stdlib/uri
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

#--
# = uri/common.rb
#
# Author:: Akira Yamada <akira@ruby-lang.org>
# Revision:: $Id$
# License::
#   You can redistribute it and/or modify it under the same term as Ruby.
#
# See URI for general documentation
#

require_relative '
    
  def self.decode_www_form(str, enc = Encoding::UTF_8, separator: '&', use__charset_: false, isindex: false)
    raise ArgumentError, "the input of #{name}.#{__method__} must be ASCII only string" unless str.ascii_only?

    ary = []
    return ary if str.empty?

    enc = Encoding.find(enc)
    str.b.each_line(separator) do |string|
      string.chomp!(separator)
      key, sep, val = string.partition('=')
      if isindex
        if sep.empty?
          val = key
          key = +''
        end
        isindex = false
      end