use stream definition for group

[cnolanminich]

Small change, but useful to show how you could use the stream_definition to determine the asset group name (similar to how we do so with dbt metadata

format of stream_definition looks like:

      # stream_definition example 
      # {'name': 's3://hooli-demo/embedded-elt/locations.csv', 'config': {'object': 'locations'}}