code: func (mb *Builder) SetMediaType(mediaType string) error {
  	if mediaType != "" && mediaType != v1.MediaTypeImageManifest {
  		return errors.New("invalid media type for OCI image manifest")
  	}
  
  	mb.mediaType = mediaType
  	return nil
  }
docs: // SetMediaType assigns the passed mediatype or error if the mediatype is not a
  // valid media type for oci image manifests currently: "" or "application/vnd.oci.image.manifest.v1+json"