class_docstr: Store a mapping from keys to multiple values with minimal overhead.
  
  Avoids storing empty collections.
code: def __init__(self) -> None:
      """ """
      self._dict = {}
  
file_path: bokeh/src/bokeh/util/datatypes.py
imports: from __future__ import annotations
  import logging
  from typing import Generic, TypeVar, cast
label_desc: Use image node_id 1 to create a new MultiValuedDict object from inherited base classes: Generic with example: obj = MultiValuedDict()