code: @Override
  	public void close() {
  		Optional<LocalTransactionContext> txContext = currentTxContext();
  		if (txContext.isPresent()) {
  			this.txCtxStack.forEach((elem) -> elem.close());
  			this.txCtxStack.clear();
  		} else {
  			this.unmanagedTransaction.ifPresent(LocalTransactionContext::close);
  		}
  	}
docs: {@inheritDoc}
  
  @see jp.co.future.uroborosql.connection.ConnectionManager#close()