code: func NewCache(backend Reader) *Cache {
  	return &Cache{
  		backend:   backend,
  		proposals: make(map[[sha256.Size]byte]*proposalInfo),
  	}
  }
docs: // Returns a Cache that wraps an underlying NameRegCacheGetter to use on a cache miss, can write to an
  // output Writer via Sync.
  // Not goroutine safe, use syncStateCache if you need concurrent access