If I selected one row in editable grid then it should deselect all other rows except selected row

Expected behaviour: If i selected one row in editable grid then it should deselect all other rows except selected row , 

Actual behaviour: It is deselecting all remaining row whenever Iam selecting any row in editable grid,

a!localVariables(
  local!selectionIndex:tointeger({}),
  local!data:{
    {id:1,name:"Pavani"},
  {id:2,name:"Sravani"},
  {id:3,name:"Srani"},
    {id:4,name:"Sri"},
  },
  a!gridLayout(
    headerCells: {
      a!gridLayoutHeaderCell(
        label: "Id"
      )
    },
    rows:a!forEach(
      items: local!data,
      expression: {
        a!gridRowLayout(
          id: fv!index,
          selectionDisabled: if(a!isNullOrEmpty(local!selectionIndex),{},
          if(count(local!selectionIndex)=fv!itemCount,false(),true())),
          contents:a!integerField(
            label: "Id",
            value: fv!item.id,
            saveInto: fv!item.id
            
           
          ),
           ),
       
      }
    ),
    selectable: true(),
    rowHeader: 1,
    
    selectionValue: local!selectionIndex,
    selectionSaveInto: a!save(
      local!selectionIndex,
     save!value
    )
   
  )
)