public NodeBlockFetcherFactory(
     INodeBlockStore nodeBlocks,
     ConcurrentChain chain,
     ILoggerFactory loggerFactory)
 {
     _nodeBlocks    = nodeBlocks;
     _chain         = chain;
     _loggerFactory = loggerFactory;
 }
 public NodeBlockFetcher(
     INodeBlockStore nodeBlocks,
     ConcurrentChain chain,
     ChainedBlock lastProcessed,
     ILoggerFactory loggerFactory)
 {
     _nodeBlocks   = nodeBlocks ?? throw new ArgumentNullException(nameof(nodeBlocks));
     _chain        = chain ?? throw new ArgumentNullException(nameof(chain));
     _logger       = loggerFactory.CreateLogger <NodeBlockFetcher>();
     ToHeight      = int.MaxValue;
     LastProcessed = lastProcessed ?? throw new ArgumentNullException(nameof(lastProcessed));
 }