datasetAnimationScopeKeys(datasetType, transition) {
    return cachedKeys(`${datasetType}.transition.${transition}`,
      () => [
        [
          `datasets.${datasetType}.transitions.${transition}`,
          `transitions.${transition}`,
        ],
        // The following are used for looking up the `animations` and `animation` keys
        [
          `datasets.${datasetType}`,
          ''
        ]
      ]);
  }
Returns the option scope keys for resolving dataset animation options.
These keys do not include the dataset itself, because it is not under options.
@param {string} datasetType
@param {string} transition
@return {string[][]}