code: def migrate_value(value):
    
    handler = {
        'histo': _migrate_histogram_value,
        'image': _migrate_image_value,
        'audio': _migrate_audio_value,
        'simple_value': _migrate_scalar_value,
    }.get(value.WhichOneof('value'))
    return handler(value) if handler else value
docs: Convert `value` to a new-style value, if necessary and possible.
  
    An "old-style" value is a value that uses any `value` field other than
    the `tensor` field. A "new-style" value is a value that uses the
    `tensor` field. TensorBoard continues to support old-style values on
    disk; this method converts them to new-style values so that further
    code need only deal with one data format.
  
    Arguments:
      value: A `Summary.Value` object. This argument is not modified.
  
    Returns:
      If the `value` is an old-style value for which there is a new-style
      equivalent, the result is the new-style value. Otherwise---if the
      value is already new-style or does not yet have a new-style
      equivalent---the value will be returned unchanged.
  
    :type value: Summary.Value
    :rtype: Summary.Value