code: func NotContainsf(t TestingT, s interface{}, contains interface{}, msg string, args ...interface{}) bool {
  	if h, ok := t.(tHelper); ok {
  		h.Helper()
  	}
  	return NotContains(t, s, contains, append([]interface{}{msg}, args...)...)
  }
docs: // NotContainsf asserts that the specified string, list(array, slice...) or map does NOT contain the
  // specified substring or element.
  //
  //    assert.NotContainsf(t, "Hello World", "Earth", "error message %s", "formatted")
  //    assert.NotContainsf(t, ["Hello", "World"], "Earth", "error message %s", "formatted")
  //    assert.NotContainsf(t, {"Hello": "World"}, "Earth", "error message %s", "formatted")