Django: how to remove delete action/button from admin

admin.py

class MyAdmin(admin.ModelAdmin):

    def has_delete_permission(self, request, obj=None):
        return False

    def get_actions(self, request):
        actions = super(MyAdmin, self).get_actions(request)
        if 'delete_selected' in actions:
            del actions['delete_selected']
        return actions