How do I use tag questions with indefinite pronouns?

For example:

Nobody came to the party, did ___?

Everybody likes him, doesn't / don't ___?

Somebody should stop her, shouldn't ____?

I would enormously appreciate your help on this.

They/them/their/etc are common and long-standing informal 3rd person genderless singular personal pronouns/adjectives.
I'd use 'they'. Does anybody else want to comment?
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Nobody came to the party, did they?
Everybody likes him, don't they?
Somebody should stop her, shouldn't they?

these are the answer for these qustions. but I can't explain these. If any one can explain pleases explain it.
Thank you
Rocky BD
 Mister Micawber's reply was promoted to an answer.
(I am not sure but I think it is correct I am not a native speaker) in the tag questions with indefinite pronouns :

(every body/one -- somebody/one -- nobody/one) ------------------------> they
nothing -----------------------------------------------------------------------------------> it

by the way be careful of the negative concept that nothing and nobody make and you must use the tag with positive concept .
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Guest ___?



2- they ?

3- they