code: func (rbds *redisBlobDescriptorService) SetDescriptor(ctx context.Context, dgst digest.Digest, desc distribution.Descriptor) error {
  	if err := dgst.Validate(); err != nil {
  		return err
  	}
  
  	if err := cache.ValidateDescriptor(desc); err != nil {
  		return err
  	}
  
  	conn := rbds.pool.Get()
  	defer conn.Close()
  
  	return rbds.setDescriptor(ctx, conn, dgst, desc)
  }
docs: // SetDescriptor sets the descriptor data for the given digest using a redis
  // hash. A hash is used here since we may store unrelated fields about a layer
  // in the future.