How does MongoDB add label field names

  mongodb, question

The Mac shell terminator command is:

> use mybook
 switched to db mybook
 
 > db.books.update ({}, {$ set: {"tags": ["essays", "essays" ]},{multi:true})
 ...

I want to add label field names, but I don’t know how to continue the command.

UseAddToSet command

db.books.updateMany({},{$addToSet:{"tags":"newTag"}})