code: func (mi *MemoryIndex) Hashes() []plumbing.Hash {
  	hashes := make([]plumbing.Hash, 0, len(mi.indexMap))
  	for k := range mi.indexMap {
  		hashes = append(hashes, k)
  	}
  	return hashes
  }
docs: // Hashes returns all the hashes that are available in the index