@Override
  public String toString() {
    return DIGEST_PREFIX + hash;
  }
Creates a new instance from a valid digest string.

@param digest the digest to generate the {@link DescriptorDigest} from
@return a new {@link DescriptorDigest} created from the digest
@throws DigestException if the digest is invalid
jib-core/src/main/java/com/google/cloud/tools/jib/api/DescriptorDigest.java