What is the correct way to set args in rosparam?

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I'm trying to launch the Multimaster node requiring parameter lists. Inside the list, I need to use an arg that would be used in other nodes in the same launch file. This is what I'd like in effect (it does not work):

  <arg name="robotname" default="robot1" />

  <node pkg="multimaster" type="master_sync.py" name="master_sync" output="screen" respawn="true"> 
    <param name="foreign_master" value="http://localhost:11311" />      
    <rosparam>
      local_pubs: [$(arg robotname)/status, /some_other_topics]
    </rosparam>
  </node>

What should be the correct way to get $(arg robotname) into the parameter list?