code: def test_ImageExporter_toBytes():
      p = pg.PlotWidget()
      p.show()
      p.hideAxis("bottom")
      p.hideAxis("left")
      exp = ImageExporter(p.getPlotItem())
      qimg = exp.export(toBytes=True)
      qimg = qimg.convertToFormat(QtGui.QImage.Format.Format_RGBA8888)
      data = fn.ndarray_from_qimage(qimg)
      black = (0, 0, 0, 255)
      assert np.all(
          data == black
      ), "Exported image should be entirely black."
  
imports: import numpy
  import pyqtgraph
  import pyqtgraph.functions
  from pyqtgraph.exporters import ImageExporter
  from pyqtgraph.Qt import QtGui
label_desc: Use image node_id 2 for calling a global function with example usage: test_ImageExporter_toBytes() without return types