public Optional<BlockHeader> lowestAnnouncedBlock() {
    return pendingBlocks.values().stream()
        .map(ImmutablePendingBlock::block)
        .map(Block::getHeader)
        .min(Comparator.comparing(BlockHeader::getNumber));
  }
Stop tracking the given block.

@param block the block that is no longer pending
@return true if this block was removed
ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/state/PendingBlocksManager.java