code: def _preprocess(self, a: np.ndarray, axis: int) -> np.ndarray:
      if len(a.shape) == 0:
          raise RuntimeError(
              f"Concat: one input has an empty shape: {a!r}."
          )
      if axis >= len(a.shape):  # type: ignore
          new_shape = a.shape + (1,) * (axis + 1 - len(a.shape))  # type: ignore
          return a.reshape(new_shape)
      return a
  
imports: import numpy
  from onnx.reference.op_run import OpRun
label_desc: Use image node_id 1 for calling the Concat obj's underlying member method code with example usage: obj._preprocess(a, axis) and returns: a, a