Picker Custom Field Error

Hey,

I am trying to configure a Picker Custom Field but am getting the following error:

"Interface Definition: Expression evaluation error at function a!pickerFieldCustom [line 290]: The function 'suggestfunction' is unavailable."

Here is my code:

a!pickerFieldCustom(
  label: "User Picker",
  placeholder: "--- Select Borrowers ---",
  labelPosition: "ABOVE", 
  suggestFunction: a!dataSubset(
    startIndex: 1,
    batchSize: -1,
    data: if(
      local!view = "Borrower",
      index(local!borrowers,"borrower",{}),
      index(local!lenders,"lender",{})
  )
  ),
  value: if(
    local!view = "Borrower",
    local!selectedBorrowers,
    local!selectedLenders
  ),
  selectedLabels: if(
    local!view = "Borrower",
    local!selectedBorrowers,
    local!selectedLenders
  ),
  saveInto: if(
    local!view = "Borrower", 
    local!selectedBorrowers,
    local!selectedLenders
  ),
  validations: {}

)

where local!borrower and local!lenders are lists of maps

Unfortunately I do not know where to start, any ideas as to how to fix this issue?