Change the inputs of an ONNX model which has N as unknown to N=1

Question

I have generated an onnx model from tensorflow and when I see the model in the "Netron" tool, it shows me the input as float32[unk__308,64,64,3] which specifies that the input rank is unknown. I have used this link as a reference (Find input shape from onnx file)

Mow, I want to change the unknown input to N=1. I am trying it using the tool sit4onnx (https://github.com/PINTO0309/sit4onnx) and below is the code but don't know what to do further like how to make changes and how to save the model after changing its input.

from sit4onnx import inference

inference(
  input_onnx_file_path="./onnx_model/spyonnx.onnx",
  fixed_shapes=[
                  [1,64,64,3]
             #     [1,101],
             #     [1,2],
                ],
  onnx_execution_provider="cpu"
)