let queryTxn = {
   "selector": {
      "param1": "value",
      "param2": "value2"
   },
   "fields": [
      "_attachments"
   ]
}

let queryTxn = {
       "selector": {
          "param1": "value",
          "param2": "value2"
       },
       "fields": [
          "attachments=true"
       ]
    }