docs: function could_phone_number_belong_to_country(phone_number, country_code, metadata)
  {
  	// Strip the leading `+`
  	const phone_number_digits = phone_number.slice('+'.length)
  
  	for (const country_phone_code of Object.keys(metadata.country_phone_code_to_countries))
  	{
  		const possible_country_phone_code = phone_number_digits.substring(0, country_phone_code.length)
  		if (country_phone_code.indexOf(possible_country_phone_code) === 0)
  		{
  			// This country phone code is possible.
  			// Does the given country correspond to this country phone code.
  			if (metadata.country_phone_code_to_countries[country_phone_code].indexOf(country_code) >= 0)
  			{
  				return true
  			}
  		}
  	}
  }