code: def execute(self, env, args):
          
  
          tasks = env.task.get_list_info()
          if not tasks:
              env.io.write("No tasks found.")
  
          else:
              if args.verbose:
                  _print_tasks(env, tasks, mark_active=True)
  
              else:
                  if env.task.active:
                      active_task = env.task.name
                  else:
                      active_task = None
  
                  for task, options, blocks in tasks:
                      if task == active_task:
                          env.io.success(task + ' *')
                      else:
                          if options is None and blocks is None:
                              env.io.error(task + ' ~')
                          else:
                              env.io.write(task)
docs: Lists all valid tasks.
  
              `env`
                  Runtime ``Environment`` instance.
              `args`
                  Arguments object from arg parser.