With a tag:

John told me that there wasn’t anyone in the office at that time,_________?

grammatical principle

determiner

When shall is used with a subject other than the first person, what does it usually indicate? Give an example.

Using extraposition:

That his invention will make people’s life more convenient is certain.

Using inversion:

Churchill was not only a statesman but also a writer.

Reinforcing the negation:

No voters approved of the education bill proposed by the senator.

Using transferred negation:

I think that the witness didn’t tell the truth.

Using a relative clause:

She is an expert I know well. She can give you some suggestions.

Using coordination:

There are many modem communication methods available today. The traditional business letters remain an important means of sending printed messages.

Using subordination:

Work hard and you will pass the grammar test in the end.