code: function decodeSessionId(sessionId) {
    var fields;
    // remove sentinal (e.g. '1_', '2_')
    sessionId = sessionId.substring(2);
    // replace invalid base64 chars
    sessionId = sessionId.replace(/-/g, '+').replace(/_/g, '/');
    // base64 decode
    if (typeof Buffer.from === 'function') {
      sessionId = Buffer.from(sessionId, 'base64').toString('ascii');
    }
    else {
      sessionId = Buffer.from(sessionId, 'base64').toString('ascii');
    }
    // separate fields
    fields = sessionId.split('~');
    return {
      apiKey: fields[1],
      location: fields[2],
      create_time: new Date(fields[3])
    };
  }
docs: /*
  decodes a sessionId into the metadata that it contains
  @param     {string}         sessionId
  @returns   {?SessionInfo}    sessionInfo