Use of array or object as ID in hook object_cache_TYPE_load()

Really nice module, exelent job!
I'm trying to cache voting API votingapi_select_single_result_value($criteria) function results, and that should not be a problem if $criteria as integer or a string, but it is an array, something like:

  $criteria = array(
    'content_type' => $type,
    'content_id' => $content_id,
    'value_type' => 'points',
    'tag' => $tag,
    'function' => 'negatives'
  );

Please provide functionality to detect $id type and convert it to string (maybe serializing and unserializing it cheking with is_object and is_array).

Or is there any other way to bypass this?