```
def group_params
  params.require(:group).permit(
    :name, 
    :description,
    group_memberships_attributes: [:id, :person_id, :_destroy]
  )
end
```
or even
```
def group_params
  params.require(:group).permit(:name, :description, group_memberships_attributes: [:id, :person_id, :_destroy])
end
```