code: def test_px_var_expand(self):
      ip = get_ipython()
      v = self.client[-1:]
      v.activate()
      v.block = True
      ip.user_ns["x"] = "client"
      v["x"] = "engine"
      ip.run_line_magic("px", 'y=f"{x}"')
      assert v["y"] == ["engine"]
  
imports: import re
  import signal
  import sys
  import time
  import pytest
  from IPython import get_ipython
  from IPython.utils.io import capture_output
  import ipyparallel
  from ipyparallel import AsyncResult
  from .clienttest import ClusterTestCase, generate_output, raises_remote
label_desc: Use image node_id 2 for calling the TestParallelMagics obj's underlying member method code with example usage: obj.test_px_var_expand() without return types