def single_format(donor, message: bool, currency_symbol: str) ->str:
    """Format string for output to text file.

    This function is for when there is only one donor or donation.    For example, for the text file holding the most recent donation.

    :param donor: Donor or Donation class object.
    :param message: If True, the message (if any) from the donor object    :param currency_symbol: The currency symbol to append to the return string.
    :returns: A string containing the inputs formatted. For example: 

    John Doe - $100.00 - Thanks for raising money for the kids.
    """
    if message:
        return (
            f'{donor.name} - {currency_symbol}{donor.amount:.2f} - {donor.message}'
            )
    else:
        return f'{donor.name} - {currency_symbol}{donor.amount:.2f}'
