def add(entries)
      entries = Array(entries)  # If entries is an array, this is a no-op.
      old_size = @entries.size
      @entries |= entries
      logger.verbose("Added #{entries.size - old_size} new entries to cache.")
    end
def add(entries)
      entries = Array(entries)  # If entries is an array, this is a no-op.
      old_size = @entries.size
      @entries |= entries
      logger.verbose("Added #{entries.size - old_size} new entries to cache.")
    end
Adds an array of objects to the cache.

 @param Array
   The entries to add.
 @return Array
   The entries after the addition.