@abc.abstractmethod<EOL><INDENT>def currency_to_string(self, amount):<DEDENT>
return<EOL>
Gets a string representation of a currency including the currency symbol indicated by the currency type.

        :param amount: a currency value
        :type amount: ``osid.financials.Currency``
        :return: the display string
        :rtype: ``string``
        :raise: ``InvalidArgument`` -- ``amount.get_currency_type() != get_currency_type()``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

        *compliance: mandatory -- This method must be implemented.*