Just doing their jobs

Someone knocked on the door, and my dog started barking.  It was the garbage man just coming for the trash.  I passed the bags out to him, but I also had some branches outside that I needed him to haul away.  So, after he got the trash up to the truck, he came back for the branches.  The dog barked at him through the door.  "He's just doing his job.  Leave him alone."  Then I thought about it: she was just doing her job by barking.