VALID(phoneNumber, { candidate, defaultCountry, metadata })
	{
		if (
			!phoneNumber.isValid() ||
			!containsOnlyValidXChars(phoneNumber, candidate, metadata)
		)
		{
			return false
		}

		// Skipped for simplicity.
		// return isNationalPrefixPresentIfRequired(phoneNumber, { defaultCountry, metadata })
		return true
	}
Phone numbers accepted are "possible" and "valid".
Numbers written in national format must have their national-prefix
present if it is usually written for a number of this type.