code: def convert_sum(node, **kwargs):
      
      name, input_nodes, attrs = get_inputs(node, kwargs)
  
      mx_axis = attrs.get("axis", None)
      axes = convert_string_to_list(str(mx_axis)) if mx_axis is not None else None
  
      keepdims = get_boolean_attribute_value(attrs, "keepdims")
  
      if axes:
          node = onnx.helper.make_node(
              'ReduceSum',
              inputs=input_nodes,
              outputs=[name],
              axes=axes,
              keepdims=keepdims,
              name=name
          )
      else:
          node = onnx.helper.make_node(
              'ReduceSum',
              inputs=input_nodes,
              outputs=[name],
              keepdims=keepdims,
              name=name
          )
      return [node]
docs: Map MXNet's sum operator attributes to onnx's ReduceSum operator
      and return the created node.