code: def test_df_kde_y():
      df = pd.DataFrame({"x": range(10), "y": range(10)})
      plot = df.vgplot.kde(y="y", bw_method="scott")
      assert plot.mark == "line"
      utils.check_encodings(
          plot, x=" ", y="Density", color=utils.IGNORE
      )
      data = plot.data
      assert set(pd.unique(data["variable"])) == {"y"}
  
imports: import pytest
  import pandas
  import altair
  from pdvega.tests import utils
label_desc: Use image node_id 28 for calling a global function with example usage: test_df_kde_y() without return types