how to get the parent node data from a detail grid

I am creating a checkbox component in a detail grid which needs to be disabled if a column value in the parent node is false.

    import { Component, OnDestroy } from '@angular/core';
    import { ICellRendererAngularComp } from '@ag-grid-community/angular-legacy';
    import { ICellRendererParams } from '@ag-grid-community/core';
    
    @Component({
      // tslint:disable-next-line: component-selector
      selector: 'checkboxRenderer',
      template: `
        <input
          type="checkbox"
          (click)="checkedHandler($event)"
          [disabled]="!params.column.isCellEditable(params.node)"
          [checked]="params.value"
        />
    `,
    })
    export class CheckboxRenderer implements ICellRendererAngularComp, OnDestroy {
    
      params: ICellRendererParams ;
      isEditable: boolean = false;
      needRefresh = true;
    
      agInit(params: ICellRendererParams): void {
        this.params = params;
    
      }
    
      checkedHandler(event: MouseEvent): void {
          const checked = (<HTMLInputElement>event.target).checked;
          const colId = this.params.column.getColId();
    
          const isEditable = this.params.column.isCellEditable(this.params.node);
    
          if (isEditable) {
            this.params.node.setDataValue(colId, checked);
            this.needRefresh = true;
          }
      }
    
      refresh(_params: any): boolean {
        const r = this.needRefresh;
        this.needRefresh = false;
        return r;
    
      }
    
      ngOnDestroy(): void {}
}

in my detailGridOptions I created a columnTypes 'billing' and created a function to define if the field is editable

     detailGridOptions: {
        columnTypes: {
          billing: {
            editable: (params: EditableCallbackParams) => {
              const invoice = params.node.parent.data;
              /*** the params.node.parent doesn't have a data ***/
              return !invoice.approved;
            },
            
          }
        },
        frameworkComponents: {
          checkbox: CheckboxRenderer,
          currency: CurrencyComponent,
        },
        columnDefs: [

          { field: 'name', headerName: 'Name' },
          { field: 'billable', headerName: 'Billable', type: 'billing', cellRenderer: 'checkbox', onCellValueChanged: this.onToggleDetailBillable.bind(this),  },
        ]
      }

My question how do I retrieve the parent node data from the detailGridOptions. I am using those packages since I am still running angular 8.2.2

"@ag-grid-community/angular-legacy": "^28.1.1",
    "@ag-grid-community/client-side-row-model": "^27.3.0",
    "@ag-grid-community/core": "^27.3.0",
    "@ag-grid-community/infinite-row-model": "^27.3.0",
    "@ag-grid-enterprise/core": "^27.3.0",
    "@ag-grid-enterprise/master-detail": "^27.3.0",
    "@ag-grid-enterprise/menu": "^27.3.0",
    "@ag-grid-enterprise/row-grouping": "^27.3.0",
    "@ag-grid-enterprise/status-bar": "^27.3.0",

Thanks

Pascal