class Faraday::Options

def fetch(key, *args)
  unless symbolized_key_set.include?(key.to_sym)
    key_setter = "#{key}="
    if args.size > 0
      send(key_setter, args.first)
    elsif block_given?
      send(key_setter, Proc.new.call(key))
    else
      raise self.class.fetch_error_class, "key not found: #{key.inspect}"
    end
  end
  send(key)
end