src/transformers/models/longformer/configuration_longformer.py/LongformerOnnxConfig/__init__
class LongformerOnnxConfig:    def __init__(self, config: "PretrainedConfig", task: str = "default", patching_specs: "List[PatchingSpec]" = None):
        super().__init__(config, task, patching_specs)
        config.onnx_export = True