src/vs/editor/contrib/snippet/browser/snippetSession.ts/SnippetSession/_move
class SnippetSession:	private _move(fwd: boolean | undefined): Selection[] {
		const selections: Selection[] = [];
		for (const snippet of this._snippets) {
			const oneSelection = snippet.move(fwd);
			selections.push(...oneSelection);
		}
		return selections;
	}