code: def current_app(self):
          
          current_focus = self.adb_shell(CURRENT_APP_CMD)
          if current_focus is None:
              return None
  
          current_focus = current_focus.replace("\r", "")
          matches = WINDOW_REGEX.search(current_focus)
  
          # case 1: current app was successfully found
          if matches:
              (pkg, activity) = matches.group("package", "activity")
              return {"package": pkg, "activity": activity}
  
          # case 2: current app could not be found
          logging.warning("Couldn't get current app, reply was %s", current_focus)
          return None
docs: Return the current app.