# File lib/openstack/compute/metadata.rb, line 51
    def update(keys=nil)
      return if @metadata.nil?
      if keys.nil?
        json = JSON.generate(:metadata => @metadata)
        response = @compute.connection.req('POST', @base_url, :data => json)
        @metadata = JSON.parse(response.body)['metadata']
      else
        keys.each { |key|
          next if not @metadata.has_key?(key)
          json = JSON.generate(:meta => { key => @metadata[key] })
          @compute.connection.req('PUT', "#{@base_url}/#{key}", :data => json)
        }
      end
    end