decodeResponses = decoder => ({
  topic: decoder.readString(),
  partitions: decoder.readArray(decodePartitions),
})
OffsetFetch Response (Version: 1) => [responses]
  responses => topic [partition_responses]
    topic => STRING
    partition_responses => partition offset metadata error_code
      partition => INT32
      offset => INT64
      metadata => NULLABLE_STRING
      error_code => INT16