CzmlDataSource EntityCollection Entity meta data

CesiumJS
1

Hello,

Please excuse me, this might be a javascript question.
I'm loading some CZML that looks like this at the header:

[
  {
    "id":"document",
  "name":"Vehicle",
    "version":"1.0",
  "_comment":"foo"
  }
...
...
...
]

When this is loaded I can listen for the event and say:
alert( arg2.name );
and pop-up the name "Vehicle" successfully.

arg2 is instance of Cesium.CzmlDataSource .

Is there a way to read the _comment attribute? We need a flexible way to put meta data into the CZML and process against it at runtime.

(sorry, not a JS programmer, but learning).

Thanks
-Tom