Map MXNet's ROIPooling operator attributes to onnx's MaxRoiPool
    operator and return the created node.

def convert_roipooling(node, **kwargs):
    """Map MXNet's ROIPooling operator attributes to onnx's MaxRoiPool
    operator and return the created node.
    """
    name, input_nodes, attrs = get_inputs(node, kwargs)

    pooled_shape = convert_string_to_list(attrs.get('pooled_size'))
    scale = float(attrs.get("spatial_scale"))

    node = onnx.helper.make_node(
        'MaxRoiPool',
        input_nodes,
        [name],
        pooled_shape=pooled_shape,
        spatial_scale=scale,
        name=name
    )
    return [node]