code: def percept(self, agent):
          
          status = if_(self.some_things_at(agent.location, Dirt),
                       'Dirty', 'Clean')
          bump = if_(agent.bump, 'Bump', 'None')
          return (status, bump)
docs: The percept is a tuple of ('Dirty' or 'Clean', 'Bump' or 'None').
          Unlike the TrivialVacuumEnvironment, location is NOT perceived.