Common modules of ros2 launch files

import os
from launch import LaunchDescription
from launch.actions import ExecuteProcess
from launch_ros.actions import Node
from launch_ros.substitutions import FindPackageShare


def generate_launch_description():
    robot_name_in_model = 'fishbot'
    package_name = 'fishbot_description'
    urdf_name = "fishbot_gazebo.urdf"

    ld = LaunchDescription()
    pkg_share = FindPackageShare(package=package_name).find(package_name) 
    urdf_model_path = os.path.join(pkg_share, f'urdf/{urdf_name}')

    #Option1: Start Gazebo server
    start_gazebo_cmd = ExecuteProcess(
        cmd=['gazebo', '--verbose', '-s', 'libgazebo_ros_factory.so'],
        output='screen')
        
   #Option2: Start Gazebo launch file
   # start_gazebo_launch = ExecuteProcess(
   #     cmd=['ros2', 'launch', 'gazebo_ros', 'gazebo.launch.py'],
   #     output='screen')

    # Launch the robot
    spawn_entity_cmd = Node(
        package='gazebo_ros', 
        executable='spawn_entity.py',
        arguments=['-entity', robot_name_in_model,  '-file', urdf_model_path ], output='screen')

    ld.add_action(start_gazebo_cmd)
   # ld.add_action(start_gazebo_launch)
    ld.add_action(spawn_entity_cmd)


    return ld