code: func NewMemStore(params *StoreParams, _ *LDBStore) (m *MemStore) {
  	if params.CacheCapacity == 0 {
  		return &MemStore{
  			disabled: true,
  		}
  	}
  
  	c, err := lru.New(int(params.CacheCapacity))
  	if err != nil {
  		panic(err)
  	}
  
  	return &MemStore{
  		cache: c,
  	}
  }
docs: //NewMemStore is instantiating a MemStore cache keeping all frequently requested
  //chunks in the `cache` LRU cache.