ag-grid : show dropdown on cell of grid with angular

I am working with angular 8 andI am able to render the ag-grid, but I also need to show the dropdown on cell, so i added the code like below :

that's a ts file code with single column.

this.columns[0] = {
  headerName: 'a', field: 'a', cellEditorParams: {
    cellEditor: 'agRichSelectCellEditor',
    values: ['a','b','c'],

  },
};
this.defaultColDef = {
  flex: 1,
  minWidth: 80,
  editable: true,
  resizable: true,
};

for html file, I have code as below :

<ag-grid-angular style="width: 100%; height: 500px;" class="ag-theme-alpine"
            [rowData]="rows" [columnDefs]="columns" (gridReady)="onGridReady($event)" [defaultColDef]="defaultColDef">

here the rows is empty, I want to show the dropdown with a,b,c as value whether the column is empty or filled with some value.

do we need to buy the enterprise edition of ag-grid to use agRichSelectCellEditor

following this tutorial