code: def test_series_line():
      ser = pd.Series([3, 2, 3, 2, 3])
      plot = ser.vgplot.line()
      utils.validate_vegalite(plot)
      assert plot.mark == "line"
      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 3 for calling a global function with example usage: test_series_line() without return types