3.代码”import os

from ament_index_python.packages import get_package_share_directory
from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch.substitutions import LaunchConfiguration
from launch_ros.actions import Node

def generate_launch_description():
fishbot_navigation2_dir = get_package_share_directory('fishbot_navigation2')
nav2_bringup_dir = get_package_share_directory('nav2_bringup')

use_sim_time = LaunchConfiguration('use_sim_time', default='true')
map_yaml_path = LaunchConfiguration('map',default=os.path.join(fishbot_navigation2_dir,'maps','room3.yaml'))
nav2_param_path = LaunchConfiguration('params_file',default=os.path.join(fishbot_navigation2_dir,'config','nav2_params.yaml'))

rviz_config_dir = os.path.join(nav2_bringup_dir,'rviz','nav2_default_view.rviz')

return LaunchDescription([
    DeclareLaunchArgument('use_sim_time',default_value=use_sim_time,description='Use simulation (Gazebo) clock if true'),
    DeclareLaunchArgument('map',default_value=map_yaml_path,description='Full path to map file to load'),
    DeclareLaunchArgument('params_file',default_value=nav2_param_path,description='Full path to param file to load'),

    IncludeLaunchDescription(
        PythonLaunchDescriptionSource([nav2_bringup_dir,'/launch','/bringup_launch.py']),
        launch_arguments={
            'map': map_yaml_path,
            'use_sim_time': use_sim_time,
            'params_file': nav2_param_path}.items(),
    ),
    Node(
        package='rviz2',
        executable='rviz2',
        name='rviz2',
        arguments=['-d', rviz_config_dir],
        parameters=[{'use_sim_time': use_sim_time}],
        outp

ut='screen'),
])“
4.不知道需要修改哪些地方，求助！！