code: @Override
      protected void writeETF(PrintWriter pw, MealyMachine<?, I, ?, O> mealy, Alphabet<I> inputs) {
          writeETFInternal(pw, mealy, inputs);
      }
docs: Write ETF parts specific for Mealy machines with IO semantics.
  
  Writes:
  - the initial state,
  - the valuations for the state ids,
  - the transitions,
  - the input alphabet (for the input labels on edges),
  - the output alphabet (for the output labels on edges).
  
  @param pw the Writer.
  @param mealy the Mealy machine to write.
  @param inputs the alphabet.