code: def _add_event_source(awsclient, evt_source, lambda_arn):
      
      event_source_obj = _get_event_source_obj(awsclient, evt_source)
  
      # (where zappa goes like remove, add)
      # we go with update and add like this:
      if event_source_obj.exists(lambda_arn):
          event_source_obj.update(lambda_arn)
      else:
          event_source_obj.add(lambda_arn)
docs: Given an event_source dictionary, create the object and add the event source.