defines possible type for a defined variable.
- "string" text sequence of characters
- "integer" signed 64-bit integer
- "datetime" static datetime or timestamp (UTC)
- "relative" relative datetime using "now+-?yMwdmsms" format (e.g. 'now-7d')
- "datapoint" hardware id, uuid or wizata_dsapi.DataPoint defining a datapoint
- "float" floating-point decimal number
- "json" complex object defined as a serializable JSON document.