docs: @Override
      public void acquireLock(StaticBuffer key, StaticBuffer column, StaticBuffer expectedValue, StoreTransaction txh) throws BackendException {
          if (locker != null) {
              ExpectedValueCheckingTransaction tx = (ExpectedValueCheckingTransaction) txh;
              if (tx.isMutationStarted())
                  throw new PermanentLockingException("Attempted to obtain a lock after mutations had been persisted");
              KeyColumn lockID = new KeyColumn(key, column);
              log.debug("Attempting to acquireLock on {} ev={}", lockID, expectedValue);
              locker.writeLock(lockID, tx.getConsistentTx());
              tx.storeExpectedValue(this, lockID, expectedValue);
          } else {
              store.acquireLock(key, column, expectedValue, unwrapTx(txh));
          }
      }