code: def test_is_tripwire():
      assert_false(is_tripwire(object()))
      assert_true(is_tripwire(TripWire("some message")))
  
imports: from dipy.utils.tripwire import TripWire, is_tripwire, TripWireError
  from dipy.testing import assert_true, assert_false
  from numpy.testing import assert_raises
label_desc: Use image node_id 1 for calling a global function with example usage: test_is_tripwire() without return types