function getNationalNumberGroups(
	metadata,
	number,
	formattingPattern
) {
	throw new Error('This part of code hasn\'t been ported')

	if (formattingPattern) {
		// We format the NSN only, and split that according to the separator.
		const nationalSignificantNumber = util.getNationalSignificantNumber(number)
		return util.formatNsnUsingPattern(nationalSignificantNumber,
																			formattingPattern, 'RFC3966', metadata).split('-')
	}

	// This will be in the format +CC-DG1-DG2-DGX;ext=EXT where DG1..DGX represents groups of digits.
	const rfc3966Format = formatNumber(number, 'RFC3966', metadata)

	// We remove the extension part from the formatted string before splitting it into different
	// groups.
	let endIndex = rfc3966Format.indexOf(';')
	if (endIndex < 0) {
		endIndex = rfc3966Format.length
	}

	// The country-code will have a '-' following it.
	const startIndex = rfc3966Format.indexOf('-') + 1
	return rfc3966Format.slice(startIndex, endIndex).split('-')
}
Helper method to get the national-number part of a number, formatted without any national
prefix, and return it as a set of digit blocks that would be formatted together following
standard formatting rules.