code: function convertOptionsParamsToIds(req, instance, options, callback) {
    var err;
  
    if(options.id) {
      var isValidID = reelib.identifier.isValid(options.id);
      if(!isValidID) {
        err = 'Invalid id';
      }
      options.ids = [options.id];
      delete options.id;
      callback(err);
    }
    else if(options.directory) {
      instance.associations.retrieveIdsByParams(req, options.directory, null,
                                                function(ids) {
        options.ids = ids;
        delete options.directory;
        callback(err);
      });
    }
    else if(options.tags) {
      instance.associations.retrieveIdsByParams(req, null, options.tags,
                                                function(ids) {
        options.ids = ids;
        delete options.tags;
        callback(err);
      });
    }
  }
docs: Convert the id, directory or tags within options to ids.
  @param {Object} req The request which originated this function call.
  @param {Chickadee} instance The given chickadee instance.
  @param {Object} options The given options.
  @param {callback} callback Function to call on completion.