code: def export() -> None:
      node = onnx.helper.make_node(
          "Erf",
          inputs=["x"],
          outputs=["y"],
      )
  
      x = np.random.randn(1, 3, 32, 32).astype(np.float32)
      y = np.vectorize(math.erf)(x).astype(np.float32)
      expect(node, inputs=[x], outputs=[y], name="test_erf")
  
file_path: onnx/onnx/backend/test/case/node/erf.py
imports: import math
  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 Erf obj's underlying member method code with example usage: obj.export() without return types