private void extractSignatures(final Block block) {
    final List<CompletableFuture<Void>> futures =
        new ArrayList<>(block.getBody().getTransactions().size());
    for (final Transaction tx : block.getBody().getTransactions()) {
      futures.add(CompletableFuture.runAsync(tx::getSender, validationExecutor));
    }
    for (final CompletableFuture<Void> future : futures) {
      future.join();
    }
  }
Import blockchain.

@param blocks the blocks
@param besuController the besu controller
@param skipPowValidation the skip pow validation
@param startBlock the start block
@param endBlock the end block
@return the rlp block importer - import result
@throws IOException the io exception
app/src/main/java/org/hyperledger/besu/chainimport/RlpBlockImporter.java