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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 last_updated(self, subpath=None):
 """ Returns the time of the last modification of the Readme or specified subpath, or None if the file does not exist. The return value is a number giving the number of seconds since the epoch (see the time module). Raises werkzeug.exceptions.NotFound if the resulting path would fall out of the root directory. """

        try:
            return os.path.getmtime(self.readme_for(subpath))
        except ReadmeNotFoundError:
            return None
        # OSError for Python 3 base class, EnvironmentError for Python 2
        except (OSError, EnvironmentError) as ex:
            if ex.errno == errno.ENOENT:
                return None
            raise