code: def test_name_prefix_join(tmpdir):
      tmpdir.chdir()
  
      def sq(x):
          return x**2
  
      wf = pe.Workflow("wf", base_dir=tmpdir.strpath)
      square = pe.Node(Function(function=sq), name="square")
      square.iterables = [("x", [1, 2])]
      square_join = pe.JoinNode(
          Merge(1, ravel_inputs=True),
          name="square_join",
          joinsource="square",
          joinfield=["in1"],
      )
      wf.connect(square, "out", square_join, "in1")
      wf.run()
  
imports: import pytest
  from ....None import config
  from ...None import engine
  from ....interfaces import base
  from ....interfaces.utility import IdentityInterface, Function, Merge
  from ....interfaces.base import traits, File
label_desc: Use image node_id 13 for calling a global function with example usage: test_name_prefix_join(tmpdir) and returns: unknown