    # File lib/fog/aws/requests/compute/modify_snapshot_attribute.rb, line 20
            def modify_snapshot_attribute(snapshot_id, attributes)
              params = {}
              params.merge!(Fog::AWS.indexed_param('CreateVolumePermission.Add.%d.Group', attributes['Add.Group'] || []))
              params.merge!(Fog::AWS.indexed_param('CreateVolumePermission.Add.%d.UserId', attributes['Add.UserId'] || []))
              params.merge!(Fog::AWS.indexed_param('CreateVolumePermission.Remove.%d.Group', attributes['Remove.Group'] || []))
              params.merge!(Fog::AWS.indexed_param('CreateVolumePermission.Remove.%d.UserId', attributes['Remove.UserId'] || []))
              request({
                'Action'        => 'ModifySnapshotAttribute',
                'SnapshotId'    => snapshot_id,
                :idempotent     => true,
                :parser         => Fog::Parsers::Compute::AWS::Basic.new
              }.merge!(params))
            end