docs: function _identity (ndate, nrandom, nchecksum, epoc) {
    // ms since EPOC (1 Jan 1970)
    var since = _getDateMillis(epoc);
  
    // Max of ndate
    if (since.length > ndate) {
      throw new Error('Date too big');
    }
  
    // Pad to ndate
    since = bitString.pad(since, ndate);
  
    // Add nrandom Random bits
    since += bitString.randomBits(nrandom);
  
    // Add checksum bits
    since += bitString.checksum(since, nchecksum);
  
    // Convert to BaseURL
    return baseURL.encode(since);
  }