    def call(__self, __context, __obj, *args, **kwargs):
        """Call an object from sandboxed code."""
        fmt = inspect_format_method(__obj)
        if fmt is not None:
            return __self.format_string(fmt, args, kwargs)

        # the double prefixes are to avoid double keyword argument
        # errors when proxying the call.
        if not __self.is_safe_callable(__obj):
            raise SecurityError('%r is not safely callable' % (__obj,))
        return __context.call(__obj, *args, **kwargs)
The software uses a function that accepts a format string as an argument, but the format string originates from an external source.