没有nav2_simple_commander，一直提示没有导入
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问题描述：
在安装的navigation2中没有nav2_simple_commander这个命令，from nav2_simple_commander.robot_navigator import BasicNavigator输入该行代码时，下面一直有波浪线，下载navigation2也是跟着教程下载的，我的版本是foxy。
具体细节和上下文：
这是终端提示的错误：Traceback (most recent call last):
File "/home/ros2/chapt7/chapt7_ws/install/fishbot_application/lib/fishbot_application/init_robot_pose", line 11, in <module>
load_entry_point('fishbot-application==0.0.0', 'console_scripts', 'init_robot_pose')()
File "/usr/lib/python3/dist-packages/pkg_resources/init.py", line 490, in load_entry_point
return get_distribution(dist).load_entry_point(group, name)
File "/usr/lib/python3/dist-packages/pkg_resources/init.py", line 2854, in load_entry_point
return ep.load()
File "/usr/lib/python3/dist-packages/pkg_resources/init.py", line 2445, in load
return self.resolve()
File "/usr/lib/python3/dist-packages/pkg_resources/init.py", line 2451, in resolve
module = import(self.module_name, fromlist=['name'], level=0)
File "/home/ros2/chapt7/chapt7_ws/install/fishbot_application/lib/python3.8/site-packages/fishbot_application/init_robot_pose.py", line 2, in <module>
from nav2_simple_commander.robot_navigator import BasicNavigator
ModuleNotFoundError: No module named 'nav2_simple_commander'尝试过的解决方法：
重新克隆nav2包，但还是不行。