a!gridRowLayout(
  contents : {
    a!integerField(
      label : "Job ID",
      value : ri!datasubset[ri!index].ID,
      readOnly : true
    ),
    a!textField(
      label : "Process Stream",
      value : ri!datasubset[ri!index].PS,
      readOnly : true
    ),
    a!textField(
      label : "Job",
      value : ri!datasubset[ri!index].Job,
      readOnly : true
    ),
    a!textField(
      label : "Task",
      value : ri!datasubset[ri!index].Task,
      readOnly : true
    ),
    a!pickerFieldGroups(
      label : "Task Assignee" ,
      maxSelections  : 1,
      value : ri!datasubset[ri!index].TaskAssignee,
      saveInto : {
        ri!subset,
        ri!datasubset[ri!index].TaskAssignee
      }
    )
  },
  id : ri!index
)




Rule Input : 
1) datasubset - type : Any Type
2) index - type : Number (Integer)
3) subset - type : Group - can store multiple values

NOte : Here I am using "datasubset", as in future I will be fetching data from one portal report. Also I have saved data of picked field in one more variable called "subset"