code: def export() -> None:
      node = onnx.helper.make_node(
          "NonZero",
          inputs=["condition"],
          outputs=["result"],
      )
  
      condition = np.array([[1, 0], [1, 1]], dtype=bool)
      result = np.array(
          np.nonzero(condition), dtype=np.int64
      )  # expected output [[0, 1, 1], [0, 0, 1]]
      expect(
          node,
          inputs=[condition],
          outputs=[result],
          name="test_nonzero_example",
      )
  
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 NonZero obj's underlying member method code with example usage: obj.export() without return types