def sfilter(self, source):
        """Filter."""

        sources = []
        if source.text[:4].encode(source.encoding) != b'PK\x03\x04':
            sources.extend(self._filter(source.text, source.context, source.encoding))
        else:
            for content, filename, enc in self.get_content(io.BytesIO(source.text.encode(source.encoding))):
                sources.extend(self._filter(content, source.context, enc))
        return sources
Filter.