code: def export() -> None:
      # Test periodic window
      node = onnx.helper.make_node(
          "BlackmanWindow",
          inputs=["x"],
          outputs=["y"],
      )
      size = np.int32(10)
      a0 = 0.42
      a1 = -0.5
      a2 = 0.08
      y = a0
      y += a1 * np.cos(
          2 * np.pi * np.arange(0, size, 1, dtype=np.float32) / size
      )
      y += a2 * np.cos(
          4 * np.pi * np.arange(0, size, 1, dtype=np.float32) / size
      )
      expect(
          node, inputs=[size], outputs=[y], name="test_blackmanwindow"
      )
  
      # Test symmetric window
      node = onnx.helper.make_node(
          "BlackmanWindow", inputs=["x"], outputs=["y"], periodic=0
      )
      size = np.int32(10)
      a0 = 0.42
      a1 = -0.5
      a2 = 0.08
      y = a0
      y += a1 * np.cos(
          2
          * np.pi
          * np.arange(0, size, 1, dtype=np.float32)
          / (size - 1)
      )
      y += a2 * np.cos(
          4
          * np.pi
          * np.arange(0, size, 1, dtype=np.float32)
          / (size - 1)
      )
      expect(
          node,
          inputs=[size],
          outputs=[y],
          name="test_blackmanwindow_symmetric",
      )
  
imports: import numpy
  import onnx
  from onnx.backend.test.case.base import Base
  from onnx.backend.test.case.node import expect
label_desc: Use image node_id 1 for calling the BlackmanWindow obj's underlying member method code with example usage: obj.export() without return types