Adding multiple people to a field with Make/Integromat

Hello everybody, I am currently working on a monday automation with Make (formerly Integromat).
I want to automatically add multiple people to a multiple people field (duh). Because Make itself only offers the option to update a field value with a single person, I am trying to add people with a GraphQL Post Request, but I have ran into some issues. Its probably, because I couldn’t figure out the correct syntax, as I am not really an expert level programmer.

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I first tested using set variables to be later replaced with variables from the other processes, but it always gives me the following error:

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Maybe someone with a bit more experience can tell me what I am doing wrong or how the query should look, because I can’t figure out what I’m doing wrong.

Thanks in advance for your answers!

EDIT: I figured it out myself, but for everyone who may be searching for the solution, I will leave the post and solution here.

The error I posted was because I had an empty line at the end of my query. But furthermore, “column_value” just needs to be named “value” and you need to define at least the id to be returned. So now my full query looks like this:

mutation {
   change_simple_column_value(
      board_id: 11111,
      item_id: 22222, 
      column_id: "people_1",
      value: "12345, 67890" 
   ) {
     id
  }
}