def _print_dict_files(self, case, target):
        """Prints the file names and available properties in the specified test case's 'target'
        dictionary.
        
        :arg case: the identifier of the test case to print contents for.
        :arg target: one of ['inputs', 'outputs', 'percent']
        """
        if case in self.live and target in self.live[case]:
            lines = []
            data = self.live[case][target]
            skeys = list(sorted(data.keys()))
            for key in skeys:
                props = ", ".join(sorted(data[key].keys()))
                lines.append("'{}': {}".format(key, props))
            return '\n'.join(lines)
        else:
            msg.err("Can't find the result set {} in {}".format(target, case))