code: def convert_Hstack(
      func, opset_version, input_names, output_names, context
  ):
      gb = onnx_helper.GraphBuilder()
      input0_ndim = len(func.inputs[0].shape)
      inputs = input_names
      axis = 1
      if input0_ndim == 0:
          inputs = [
              gb.op("Unsqueeze", [name], axes=[0])
              for name in input_names
          ]
          axis = 0
      elif input0_ndim == 1:
          axis = 0
      gb.op_output_named("Concat", inputs, output_names, axis=axis)
      return gb.nodes()
  
imports: import warnings
  import chainer
  import numpy
  import onnx
  from onnx.mapping import NP_TYPE_TO_TENSOR_TYPE
  from onnx_chainer.functions.opset_version import support
  from onnx_chainer import onnx_helper
label_desc: Use image node_id 23 for calling a global function with example usage: convert_Hstack(func, opset_version, input_names, output_names, context) and returns: gb