<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def backing_file(self):
 """ When using linked clone this will return the path to the base image :returns: None if it's not a linked clone, the path otherwise """


        with open(self._path, 'rb') as f:
            f.seek(self.backing_file_offset)
            content = f.read(self.backing_file_size)

        path = content.decode()
        if len(path) == 0:
            return None
        return path