launch file

import launch
from launch.substitutions import Command, LaunchConfiguration
import launch_ros
import os

def generate_launch_description():
    pkg_share = launch_ros.substitutions.FindPackageShare(package='sam_bot_description').find('sam_bot_description')
    default_model_path = os.path.join(pkg_share, 'src/description/aroc_truck_description.urdf')
    default_rviz_config_path = os.path.join(pkg_share, 'rviz/urdf_config.rviz')

    robot_state_publisher_node = launch_ros.actions.Node(
        package='robot_state_publisher',
        executable='robot_state_publisher',
        parameters=[{'robot_description': Command(['xacro ', LaunchConfiguration('model')])}]
    )
    joint_state_publisher_node = launch_ros.actions.Node(
        package='joint_state_publisher',
        executable='joint_state_publisher',
        name='joint_state_publisher',
        condition=launch.conditions.UnlessCondition(LaunchConfiguration('gui'))
    )
    joint_state_publisher_gui_node = launch_ros.actions.Node(
        package='joint_state_publisher_gui',
        executable='joint_state_publisher_gui',
        name='joint_state_publisher_gui',
        condition=launch.conditions.IfCondition(LaunchConfiguration('gui'))
    )
    rviz_node = launch_ros.actions.Node(
        package='rviz2',
        executable='rviz2',
        name='rviz2',
        output='screen',
        arguments=['-d', LaunchConfiguration('rvizconfig')],
    )

    spawn_entity = launch_ros.actions.Node(
        package='gazebo_ros',
        executable='spawn_entity.py',
        arguments=['-entity', 'sam_bot', '-topic', 'robot_description'],
        output='screen'
    )

    robot_localization_node = launch_ros.actions.Node(
       package='robot_localization',
       executable='ekf_node',
       name='ekf_filter_node',
       output='screen',
       parameters=[os.path.join(pkg_share, 'config/ekf.yaml'), {'use_sim_time': LaunchConfiguration('use_sim_time')}]
)

    return launch.LaunchDescription([
        launch.actions.DeclareLaunchArgument(name='gui', default_value='True',
                                            description='Flag to enable joint_state_publisher_gui'),
        launch.actions.DeclareLaunchArgument(name='model', default_value=default_model_path,
                                            description='Absolute path to robot urdf file'),
        launch.actions.DeclareLaunchArgument(name='rvizconfig', default_value=default_rviz_config_path,
                                            description='Absolute path to rviz config file'),
        launch.actions.ExecuteProcess(cmd=['gazebo', '--verbose', '-s', 'libgazebo_ros_init.so', '-s', 'libgazebo_ros_factory.so'], output='screen'),
        launch.actions.DeclareLaunchArgument(name='use_sim_time', default_value='True',
                                            description='Flag to enable use_sim_time'),
        joint_state_publisher_node,
        joint_state_publisher_gui_node,
        robot_state_publisher_node,
        spawn_entity,
        robot_localization_node,
        rviz_node
    ])