code: def test_series_bar():
      ser = pd.Series([4, 5, 4, 5], index=["A", "B", "C", "D"])
      plot = ser.vgplot.bar()
      utils.validate_vegalite(plot)
      assert plot.mark == "bar"
      utils.check_encodings(plot, x="index", y="0")
  
imports: import pytest
  import pandas
  import altair
  from pdvega.tests import utils
label_desc: Use image node_id 11 for calling a global function with example usage: test_series_bar() without return types