关于类名的问题

3-13的示例中有一段这样的代码

<div class="form-group has-success">

为什么在bootstrap的css文件中没有找到这样的一个类名设置，跟has-success有关的类名只有下面这几类

has-success .help-block,

Line 2814: .has-success .control-label,

Line 2815: .has-success .radio,

Line 2816: .has-success .checkbox,

Line 2817: .has-success .radio-inline,

Line 2818: .has-success .checkbox-inline,

Line 2819: .has-success.radio label,

Line 2820: .has-success.checkbox label,

Line 2821: .has-success.radio-inline label,

Line 2822: .has-success.checkbox-inline label {

Line 2825: .has-success .form-control {

Line 2830: .has-success .form-control:focus {

Line 2835: .has-success .input-group-addon {

Line 2840: .has-success .form-control-feedback {