code: def step_all(self):
      assert_equals(self.non_modified_passdown, "a")
  
imports: from metaflow_test import MetaflowTest, ExpectationFailed, steps
label_desc: Use image node_id 4 for calling the MergeArtifactsPropagationTest obj's underlying member method code with example usage: obj.step_all() without return types