The package installation also mounts an instance of itself under the dotlrn-catalog url, here another amp-callback-proc is called (after-mount) to create the category tree that will allow to categorize each course in different ways. The category tree is created as follows:

# To categorize courses 
      set tree_id [category_tree::add -name "dotlrn-course-catalog"] 
      category_tree::map -tree_id $tree_id -object_id $package_id -assign_single_p "t"