Function getDataSourceAttributes

getDataSourceAttributes(layerId): Promise<JDataSourceAttribute[]>
JMap.Layer.getDataSourceAttributes

Returns the attributes of the associated datasource, for a given layer.
Parameters
- layerId: JId
  the JMap layer id
Returns Promise<JDataSourceAttribute[]>
Throws
if layerId not valid or dataSource not found

Example
```
// Returns datasource attributes, for layer id=3
JMap.Layer
 .getDataSourceAttributes(3)
```