code: public <E> long increment(PartitionKey key, String fieldName, long amount,
        EntityMapper<E> entityMapper) {
      Increment increment = entityMapper.mapToIncrement(key, fieldName, amount);
      HTableInterface table = pool.getTable(tableName);
      Result result;
      try {
        result = table.increment(increment);
      } catch (IOException e) {
        throw new DatasetIOException("Error incrementing field.", e);
      }
      return entityMapper.mapFromIncrementResult(result, fieldName);
  
    }
docs: Execute an increment on an entity field. This field must be a type that
  supports increments. Returns the new increment value of type long.
  
  @param key
  The key to map to an Increment
  @param fieldName
  The name of the field we are incrementing
  @param amount
  The amount to increment by
  @param entityMapper
  The EntityMapper to map the key and increment amount to an
  Increment.
  @return The new field amount after the increment.