code: function encode(source, label) {
    if (!Buffer.isBuffer(source)) {
      throw new TypeError('Argument `source` should be a Buffer.')
    }
  
    if (typeof label !== 'string') {
      throw new TypeError('Argument `label` should be a string in upper case.')
    }
  
    const prefix = before + ' ' + label + endline
    const suffix = after + ' ' + label + endline
  
    const body = source.toString('base64').replace(/(.{64})/g, '$1\r\n')
  
    return [prefix, body, suffix].join('\r\n')
  }
docs: Convert data to PEM format.
  @param {Buffer} source
  @param {string} label
  @returns {String}