docs: def _load_cube_pkg(pkg, cube):
      '''
      NOTE: all items in fromlist must be strings
      '''
      try:
          # First, assume the cube module is available
          # with the name exactly as written
          fromlist = map(str, [cube])
          mcubes = __import__(pkg, fromlist=fromlist)
          return getattr(mcubes, cube)
      except AttributeError:
          # if that fails, try to guess the cube module
          # based on cube 'standard naming convention'
          # ie, group_cube -> from group.cube import CubeClass
          _pkg, _mod, _cls = cube_pkg_mod_cls(cube)
          fromlist = map(str, [_cls])
          mcubes = __import__('%s.%s.%s' % (pkg, _pkg, _mod),
                              fromlist=fromlist)
          return getattr(mcubes, _cls)