<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def tmpdir(self):
 """The temporary directory in which igraph is downloaded and extracted."""

        if self._tmpdir is None:
            self._tmpdir = tempfile.mkdtemp(prefix="igraph.")
            atexit.register(cleanup_tmpdir, self._tmpdir)
        return self._tmpdir