def validate(entries)
      logger.verbose("Validating #{entries.size} possible cache matches.")
      valid_entries = entries.group_by(&:validate)
      @token_cache.remove(valid_entries[false] || [])
      valid_entries[true] || []
    end
def validate(entries)
      logger.verbose("Validating #{entries.size} possible cache matches.")
      valid_entries = entries.group_by(&:validate)
      @token_cache.remove(valid_entries[false] || [])
      valid_entries[true] || []
    end
Checks if an array of current cache entries are still valid, attempts to
 refresh those that have expired and discards those that cannot be.

 @param Array[CachedTokenResponse] entries
   The tokens to validate.
 @return Array[CachedTokenResponse]