public Optional<Integer> getOmmerCount(final Hash blockHeaderHash) {
    return blockchain.getBlockBody(blockHeaderHash).map(b -> b.getOmmers().size());
  }
Returns the number of ommers in the block at the given height.

@param blockHeaderHash The hash of the block being queried.
@return The number of ommers in the referenced block.
ethereum/api/src/main/java/org/hyperledger/besu/ethereum/api/query/BlockchainQueries.java