code: def _get_index_list_of_values(d, k, def_value=None):
      
      v = d.get(k, def_value)
      if v is None:
          return []
      if isinstance(v, list):
          return v
      return [v]
docs: Like _index_list_of_values, but uses get to access and
      returns an empty list if the key is absent.
      Returns d[k] or [d[k]] if the value is not a list