# File lib/fog/aws/requests/rds/download_db_logfile_portion.rb, line 35
        def download_db_logfile_portion(identifier=nil, filename=nil, opts={})
          response = Excon::Response.new
          server_set = []
          if identifier
            if server = self.data[:servers][identifier]
              server_set << server
            else
              raise Fog::AWS::RDS::NotFound.new("DBInstance #{identifier} not found")
            end
          else
            server_set = self.data[:servers].values
          end

          response.status = 200
          response.body = {
              "ResponseMetadata" => { "RequestId"=> Fog::AWS::Mock.request_id },
              "DescribeDBInstancesResult" => { "DBInstances" => server_set }
          }
          response
        end