How to add USD file in stage thru connector code

I saw the video about adding the material on existing USD object in stage.(https://www.youtube.com/watch?v=McqjFelLCAE)
but is there any API I can use to open the USD file I want? then continue to change properties.
for example : i run the connector code, it add the usd file i choosed in empty stage, then change its material properties.
Is that “UsdStage::Open”? would it replace the original stage?
thank you