Create a transducer which realizes a partial identity for the series recognized by the input automaton. It means that the transducer will accept the same series as the input automaton, and for each input word $w$ the output will be $w$.
The following is the input automaton:
a = vcsn.Q.expression("<3>abc*(<2>d)* + ce<5>").automaton() a
b = a.partial_identity() b