code: func (b *DynamoDBBackend) Create(ctx context.Context, item backend.Item) (*backend.Lease, error) {
  	err := b.create(ctx, item, modeCreate)
  	if trace.IsCompareFailed(err) {
  		err = trace.AlreadyExists(err.Error())
  	}
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	return b.newLease(item), nil
  }
docs: // Create creates item if it does not exist