Constituent service is an important part of a public servant’s job, and some do it better than others. Attorney General Maura Healey apparently has it down. This week, Kay Hanley, frontwoman for the band Letters to Cleo, was trying to reach Healey and tweeted: “Anybody know how to put me in touch with MA AG @maura_healey?’’ A few hours later, Hanley said she was all set. “Not for nothing but I heard back from @MassAGO’s peeps in MINUTES,’’ she tweeted. “When @maura_healey runs for Governor I’ll totally write her theme song.’’