code: def test_fill_value():
      td = TabularData(["col-1", "col-2", "col-3"], fill_value="?")
      td.append(["foo"])
      assert list(td) == [["foo", "?", "?"]]
  
      td.extend(
          [
              ["bar"],
              ["foobar", "foobar2"],
              ["f", "fo", "foo", "foob", "fooba", "foobar"],
          ]
      )
      assert list(td) == [
          ["foo", "?", "?"],
          ["bar", "?", "?"],
          ["foobar", "foobar2", "?"],
          ["f", "fo", "foo"],
      ]
  
      td.insert(1, ["lorem"])
      assert td[1] == ["lorem", "?", "?"]
  
      td[0] = ["lorem", "ipsum"]
      assert td[0] == ["lorem", "ipsum", "?"]
  
      td[1:2] = [["f", "fo"]]
      assert td[1:2] == [["f", "fo", "?"]]
  
      td.add_column("col-4")
      assert td.keys() == ["col-1", "col-2", "col-3", "col-4"]
      assert td[0][3] == "?"
  
file_path: dvc/tests/unit/test_tabular_data.py
imports: import pytest
  from dvc.compare import TabularData
label_desc: Use image node_id 4 for calling a global function with example usage: test_fill_value() without return types