code: def _begin(size, periodic, output_datatype):  # type: ignore
      dtype = tensor_dtype_to_np_dtype(output_datatype)
      if periodic == 1:
          N_1 = size
      else:
          N_1 = size - 1
      ni = np.arange(size, dtype=dtype)
      return ni, N_1
  
imports: import numpy
  from onnx.helper import tensor_dtype_to_np_dtype
  from onnx.reference.op_run import OpRun
label_desc: Use image node_id 1 for calling the _CommonWindow obj's underlying member method code with example usage: obj._begin(size, periodic, output_datatype) and returns: ni,  N_1