code: def create_payload(self):
          
          data = super(SyncPlan, self).create_payload()
          if isinstance(data.get('sync_date'), datetime):
              data['sync_date'] = data['sync_date'].strftime('%Y-%m-%d %H:%M:%S')
          return data
docs: Convert ``sync_date`` to a string.
  
          The ``sync_date`` instance attribute on the current object is not
          affected. However, the ``'sync_date'`` key in the dict returned by
          ``create_payload`` is a string.