code: def find_duplicate_items(items, k=2):
      r
      import utool as ut
      # Build item histogram
      duplicate_map = ut.ddict(list)
      for count, item in enumerate(items):
          duplicate_map[item].append(count)
      # remove singleton items
      singleton_keys = []
      for key in six.iterkeys(duplicate_map):
          if len(duplicate_map[key]) == 1:
              singleton_keys.append(key)
      for key in singleton_keys:
          del duplicate_map[key]
      duplicate_map = dict(duplicate_map)
      return duplicate_map
docs: r"""
      Args:
          items (list):
  
      Returns:
          dict: duplicate_map of indexes
  
      CommandLine:
          python -m utool.util_list --test-find_duplicate_items
  
      Example:
          >>> # DISABLE_DOCTEST
          >>> from utool.util_list import *  # NOQA
          >>> items = [0, 1, 2, 3, 3, 0, 12, 2, 9]
          >>> duplicate_map = find_duplicate_items(items)
          >>> result = str(duplicate_map)
          >>> print(result)