What's the data format of Athena's .csv.me

Question

What's the data format of the .csv.metadata files written by Amazon Athena?

Alongside the output file of every query there is a metadata file. It looks like it describes the schema of the result. I assume this is what Athena uses to create the ResultSet.ResultSetMetadata part of the response of GetQueryResults requests, and that it is somehow created by Hive or Presto.

2019-04-23 14:51:29         27 e7629796-9b91-476a-bfb7-2fe6c9595bce.csv
2019-04-23 14:51:29         56 e7629796-9b91-476a-bfb7-2fe6c9595bce.csv.metadata
2019-04-27 14:23:53    1591958 ebe432ac-db7b-4ea1-b5de-529350d1a02a.csv
2019-04-27 14:23:53        712 ebe432ac-db7b-4ea1-b5de-529350d1a02a.csv.metadata
2019-04-25 16:31:23      10152 eeb6f4ab-9ac3-4a7e-81c4-0cc155187acb.csv
2019-04-25 16:31:23        494 eeb6f4ab-9ac3-4a7e-81c4-0cc155187acb.csv.metadata
2019-04-25 22:30:56   22384376 f0160ff7-e5b3-466d-926a-a660a5208c5f.csv
2019-04-25 22:30:56        494 f0160ff7-e5b3-466d-926a-a660a5208c5f.csv.metadata

Here's a hexdump of e7629796-9b91-476a-bfb7-2fe6c9595bce.csv.metadata from the listing above:

00000000  0a 1b 32 30 31 39 30 34  32 33 5f 31 32 35 31 32  |..20190423_12512|
00000010  38 5f 30 30 30 30 31 5f  65 68 74 75 72 22 19 0a  |8_00001_ehtur"..|
00000020  04 68 69 76 65 22 03 61  72 79 2a 03 61 72 79 32  |.hive".ary*.ary2|
00000030  05 61 72 72 61 79 48 03                           |.arrayH.|

It's ResultSet.ResultSetMetadata looks like this:

"ResultSetMetadata": {
  "ColumnInfo": [
    {
      "CatalogName": "hive",
      "SchemaName": "",
      "TableName": "",
      "Name": "ary",
      "Label": "ary",
      "Type": "array",
      "Precision": 0,
      "Scale": 0,
      "Nullable": "UNKNOWN",
      "CaseSensitive": false
    }
  ]
}

I realise that these are internal file to Athena, but I'm curious.