@Override
  protected CompletableFuture<Map<BlockHeader, List<TransactionReceipt>>> executePeerTask(
      final Optional<EthPeer> assignedPeer) {
    return requestReceipts(assignedPeer).thenCompose(this::processResponse);
  }
Given a set of headers, repeatedly requests the receipts for those blocks.
ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/tasks/GetReceiptsForHeadersTask.java