code: func ParsePEM(data, header string) ([]byte, error) {
  	block, rest := pem.Decode([]byte(data))
  	if len(rest) != 0 || block == nil {
  		return nil, fmt.Errorf("not a valid %q PEM", header)
  	}
  	if block.Type != header {
  		return nil, fmt.Errorf("expecting %q, got %q", header, block.Type)
  	}
  	return block.Bytes, nil
  }
docs: // ParsePEM takes pem-encoded block and decodes it, checking the header.