How it's supposed that workspace works?

In my package I’m opening a new workspace using atom.workspace.open(uri) and later if the user wants to open a new workspace I want to make sure that it doesn’t open the same again so I want to destroy the old one.

const pane = atom.workspace.paneForURI(uri)

if (pane) {
    pane.destroyItem(pane)
}

pane is always undefined so, how I’m suppose that I can find it?