code: func (b *DynamoDBBackend) Put(ctx context.Context, item backend.Item) (*backend.Lease, error) {
  	err := b.create(ctx, item, modePut)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	return b.newLease(item), nil
  }
docs: // Put puts value into backend (creates if it does not
  // exists, updates it otherwise)