<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def mold_id_to_path(self, mold_id, default=_marker):
 """ Lookup the filesystem path of a mold identifier. """


        def handle_default(debug_msg=None):
            if debug_msg:
                logger.debug('mold_id_to_path:' + debug_msg, mold_id)
            if default is _marker:
                raise KeyError(
                    'Failed to lookup mold_id %s to a path' % mold_id)
            return default

        result = self.molds.get(mold_id)
        if result:
            return result

        if not self.tracked_entry_points:
            return handle_default()

        try:
            prefix, mold_basename = mold_id.split('/')
        except ValueError:
            return handle_default(
                'mold_id %s not found and not in standard format')

        entry_point = self.tracked_entry_points.get(prefix)
        if entry_point is None:
            return handle_default()
        return join(self._entry_point_to_path(entry_point), mold_basename)