code: func NewSeededFormats(seeds []knownFormat, normalizer NameNormalizer) Registry {
  	if normalizer == nil {
  		normalizer = DefaultNameNormalizer
  	}
  	// copy here, don't modify original
  	d := append([]knownFormat(nil), seeds...)
  	return &defaultFormats{
  		data:          d,
  		normalizeName: normalizer,
  	}
  }
docs: // NewSeededFormats creates a new formats registry