docs: def unflat_map(func, unflat_items, vectorized=False, **kwargs):
      r"""
      Uses an ibeis lookup function with a non-flat rowid list.
      In essence this is equivilent to [list(map(func, _items)) for _items in unflat_items].
      The utility of this function is that it only calls method once.
      This is more efficient for calls that can take a list of inputs
  
      Args:
          func (func): function
          unflat_items (list): list of rowid lists
  
      Returns:
          list of values: unflat_vals
  
      CommandLine:
          python -m utool.util_list --test-unflat_map
  
      Example:
          >>> # ENABLE_DOCTEST
          >>> from utool.util_list import *  # NOQA
          >>> vectorized = False
          >>> kwargs = {}
          >>> def func(x):
          >>>     return x + 1
          >>> unflat_items = [[], [1, 2, 3], [4, 5], [6, 7, 8, 9], [], []]
          >>> unflat_vals = unflat_map(func, unflat_items)
          >>> result = str(unflat_vals)
          >>> print(result)
          [[], [2, 3, 4], [5, 6], [7, 8, 9, 10], [], []]
      """
      import utool as ut
      # First flatten the list, and remember the original dimensions
      flat_items, reverse_list = ut.invertible_flatten2(unflat_items)
      # Then preform the lookup / implicit mapping
      if vectorized:
          # func is vectorized
          flat_vals = func(flat_items, **kwargs)
      else:
          flat_vals = [func(item, **kwargs) for item in flat_items]
      if True:
          assert len(flat_vals) == len(flat_items), (
              'flat lens not the same, len(flat_vals)=%d len(flat_items)=%d' %
              (len(flat_vals), len(flat_items),))
      # Then ut.unflatten2 the results to the original input dimensions
      unflat_vals = ut.unflatten2(flat_vals, reverse_list)
      if True:
          assert len(unflat_vals) == len(unflat_items), (
              'unflat lens not the same, len(unflat_vals)=%d len(unflat_rowids)=%d' %
              (len(unflat_vals), len(unflat_items),))
      return unflat_vals