@abc.abstractmethod<EOL><INDENT>def convert_format(self, source_text):<DEDENT>
return<EOL>
Converts a format.

        :param source_text: the string to convert
        :type source_text: ``string``
        :return: the resulting string
        :rtype: ``string``
        :raise: ``InvalidArgument`` -- ``source_text`` not of source format
        :raise: ``NullArgument`` -- ``source_text`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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