old_contents: from flow.protocol.message import Message
  
  class UpdateMessage(Message):
      required_fields = {
              'net_key': basestring,
              'operation_id': int,
              'name': basestring,
              'workflow_plan_id': int,
       }
  
      optional_fields = {
              'parent_net_key': basestring,
              'parent_operation_id': int,
              'peer_net_key': basestring,
              'peer_operation_id': int,
              'parallel_index': int,
              'is_subflow': bool,
              'status': basestring,
              'dispatch_id': basestring,
              'user_name': basestring,
              'start_time': basestring,
              'end_time': basestring,
              'stdout': basestring,
              'stderr': basestring,
              'exit_code': int,
      }
  
new_contents: from flow.protocol.message import Message
  
  class UpdateMessage(Message):
      required_fields = {
              'net_key': basestring,
              'operation_id': int,
              'name': basestring,
              'workflow_plan_id': int,
       }
  
      optional_fields = {
              'parent_net_key': basestring,
              'parent_operation_id': int,
              'peer_net_key': basestring,
              'peer_operation_id': int,
              'parallel_index': int,
              # is this a subworkflow: i.e. DV2, etc.
              # obviously we can't inspect environment variables here to determine
              # that.
              'is_subflow': bool,
              'status': basestring,
              'dispatch_id': basestring,
              'user_name': basestring,
              'start_time': basestring,
              'end_time': basestring,
              'stdout': basestring,
              'stderr': basestring,
              'exit_code': int,
      }
  
subject: add clarifying comment