name 'joint' is not defined (Xacro)

edit

I'm basically trying to run a robot self filter package (https://github.com/blodow/realtime_ur...) with a robot urdf.xacro file (https://github.com/ToyotaResearchInst...).

This is the launch file I changed to run the filter with the specific urdf.xacro:

<launch>
  <!-- args -->
  <arg name="robot" default="hsrb4s"/>

  <node pkg="realtime_urdf_filter" type="realtime_urdf_filter" name="$(anon realtime_urdf_filter)" output="screen"> 
   <remap from="~input_depth" to="/hsrb/head_rgbd_sensor/depth_registered/image_rect_raw"/>
   <remap from="~output_depth" to="/hsrb/head_rgbd_sensor/depth_registered_filtered/image_rect" />
   <remap from="~output_mask" to="/urdf_filtered_mask" />

   <rosparam command="load" file="$(find realtime_urdf_filter)/launch/filter_parameters.yaml"/>
  </node>

 <!-- Load an example URDF -->
 <param name="robot_description" command="$(find xacro)/xacro '$(find realtime_urdf_filter)/robots/$(arg robot).urdf.xacro'"/>
 <node name="joint_state_publisher" pkg="joint_state_publisher" type="joint_state_publisher" />
 <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher" />

</launch>

I also changed the name of the package in the original xarco files so that it fits to the robot self filter package. And when I ran this launch file, I get the following error:

name 'joint' is not defined
when evaluating expression 'joint'
when processing file: /home/user/catkin_ws/src/realtime_urdf_filter/urdf/common.xacro
included from: /home/user/catkin_ws/src/realtime_urdf_filter/robots/hsrb4s.urdf.xacro
RLException: Invalid <param> tag: Cannot load command parameter [robot_description]: command [['/opt/ros/noetic/lib/xacro/xacro', '/home/user/catkin_ws/src/realtime_urdf_filter/robots/hsrb4s.urdf.xacro']] returned with code [2]. 
Param xml is <param name="robot_description" command="$(find xacro)/xacro '$(find realtime_urdf_filter)/robots/$(arg robot).urdf.xacro'"/>
The traceback for the exception was written to the log file

This is the file which the error message is directing:

<?xml version="1.0"?>
<robot xmlns:xacro="http://ros.org/wiki/xacro">

  <xacro:arg name="implicit_damping" default="false" />

  <xacro:property name="pi" value="3.14159265359"/>

  <macro name="hsrb_position_joint_transmission" params="joint reduction">
     <transmission name="${joint}_transmission">
       <type>transmission_interface/SimpleTransmission</type>
       <joint name="${joint}">
         <hardwareInterface>PositionJointInterface</hardwareInterface>
       </joint>
       <actuator name="${joint}_actuator">
         <hardwareInterface>PositionJointInterface</hardwareInterface>
         <mechanicalReduction>${reduction}</mechanicalReduction>
       </actuator>
     </transmission>
  </macro>

  <macro name="hsrb_effort_joint_transmission" params="joint reduction">
     <transmission name="${joint}_transmission">
       <type>transmission_interface/SimpleTransmission</type>
       <joint name="${joint}">
         <hardwareInterface>EffortJointInterface</hardwareInterface>
       </joint>
       <actuator name="${joint}_actuator">
         <hardwareInterface>EffortJointInterface</hardwareInterface>
         <mechanicalReduction>${reduction}</mechanicalReduction>
       </actuator>
     </transmission>
  </macro>

  <macro name="hsrb_velocity_joint_transmission" params="joint reduction">
      <transmission name="${prefix}_transmission">
          <type>transmission_interface/SimpleTransmission</type>
          <joint name="${joint}">
            <hardwareInterface>VelocityJointInterface</hardwareInterface>
          </joint>
          <actuator name="${joint}_actuator">
              <hardwareInterface>VelocityJointInterface</hardwareInterface>
              <mechanicalReduction>${reduction}</mechanicalReduction>
          </actuator>
      </transmission>
  </macro>
.......etc
</robot>

Can somebody help me understand what the error is indicating and how to tweak things to resolve this issue?

I wonder whether version matters here since I'm using Noetic while the robot description was generated several years ago.