creating a unique list

Hello, I'm reading a record that contains a text field I'd like to have listed in an array. However, the array should only have unique values, so if that text is already in there, I don't need to add it again. I've written this. 

a!localVariables(
  local!arrayOfMakes,
  a!forEach(
    items: a!queryRecordType(
      recordtype: recordType!KD VM Vehicle,
      fields: recordType!KD VM Vehicle.fields.make,
      pagingInfo: a!pagingInfo(
        startindex: 1,
        batchSize: 50)
    ).data[recordType!KD VM Vehicle.fields.make],
    expression: 
    if(
      contains(local!arrayOfMakes, fv!item), null,
      append(local!arrayOfMakes, fv!item) 
    )
  )
)

It returns what I think I need, but it's not unique. Here's part of the output. Further down you would see that it has several entries for the same make. 

All ideas are appreciated!

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