code: def test_custom_ylabel(self):
      overlay = Overlay(
          [
              Curve(range(10), label=f"Data {i}").opts(
                  subcoordinate_y=True
              )
              for i in range(2)
          ]
      )
      overlay.opts(ylabel="Y label")
      plot = bokeh_renderer.get_plot(overlay)
      # the figure axis has the label set
      assert plot.state.yaxis.axis_label == "Y label"
      # the ticks show the labels
      assert plot.state.yaxis.ticker.ticks == [0, 1]
      assert plot.state.yaxis.major_label_overrides == {
          0: "Data 0",
          1: "Data 1",
      }
  
imports: import numpy
  import pytest
  from bokeh.models.tools import WheelZoomTool, ZoomInTool, ZoomOutTool
  from holoviews.core import Overlay
  from holoviews.element import Curve
  from holoviews.element.annotation import VSpan
  from .test_plot import TestBokehPlot, bokeh_renderer
label_desc: Use image node_id 7 for calling the TestSubcoordinateY obj's underlying member method code with example usage: obj.test_custom_ylabel() without return types