Load and Unload Model

Well am new to this world of webGL and don’t know much about it and I chose to learn playcanvas as it was the most exciting tool I found but I got stuck at a place where I could not find any way to unload my model from the screen by the code and same for load it again
if someone help please
if someone share any project or the whole code not the chunk of the code so i get to know the whole concept
and it does not matter if it is being loaded by the ID or the reference of the model
the model is in the project as i start the project the model is in the scene and i want to unload it by clicking any key or button or mouse and then load it again from the reference not from the memory but from the file of asset.