class Google::Cloud::Config

def reset! key = nil
  if key.nil?
    @values.each_key { |k| reset! k }
  else
    key = key.to_sym
    if @defaults.key? key
      @values[key] = @defaults[key]
      @values[key].reset! if @validators[key] == SUBCONFIG
    elsif @values.key? key
      warn! "Key #{key.inspect} has not been added, but has a value." \
            " Removing the value."
      @values.delete key
    else
      warn! "Key #{key.inspect} does not exist. Nothing to reset."
    end
  end
  self
end