How to get shape of FunctionalTensor?

Unity Engine
,
1

I want to Reshape FunctionalTensor using Functional.Reshape().
For this purpose, I want to get shape of source FunctionalTensor.
However, FunctionalTensor does not seem to have a shape member like a Tensor.
How to get original shape of FunctionalTensor?
Any good ways to make this?

var graph = new FunctionalGraph();
var inputs = graph .AddInputs(model);
var outputs = graph .Forward(model, inputs);

var output = outputs[0];
var shape = /* how to get shape of output? */
var reshaped_output = output.Reshape(new int[3] { shape[0], shape[1] * shape[2], shape[3] }); // e.g. (dim0, dim1, dim2, dim3) -> (dim0, dim1 * dim2, dim3)

var edited_model = graph.Compile(reshaped_output);