code: def get_implicit_deps(self):
          
          result = []
          build_env = self.get_build_env()
          for act in self.get_action_list():
              deps = act.get_implicit_deps(self.get_all_targets(),
                                           self.get_all_sources(),
                                           build_env)
              result.extend(deps)
          return result
docs: Return the executor's implicit dependencies, i.e. the nodes of
          the commands to be executed.