docs: def list_installed():
      '''
      Return a list of all installed kernels.
  
      CLI Example:
  
      .. code-block:: bash
  
          salt '*' kernelpkg.list_installed
      '''
      result = __salt__['pkg.version'](_package_name(), versions_as_list=True)
      if result is None:
          return []
  
      if six.PY2:
          return sorted(result, cmp=_cmp_version)
      else:
          return sorted(result, key=functools.cmp_to_key(_cmp_version))