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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _parse_known_pattern(self, pattern: str) -> List[str]: """ Expand pattern if identified as a directory and return found sub packages """

        if pattern.endswith(os.path.sep):
            patterns = [
                filename
                for filename in os.listdir(pattern)
                if os.path.isdir(os.path.join(pattern, filename))
            ]
        else:
            patterns = [pattern]

        return patterns