Cannot work with CSS Modules about composition-api HOT 4 CLOSED

<script>
  import { onBeforeMount } from '@vue/composition-api';
  export default {
    setup() {
      const css = { $a, $b, $style };
      onBeforeMount(function(){
        ({ $a: css.$a, $b: css.$b, $style: css.$style } = this);
      });
      // css.$a, css.$b, css.$style are now available for use in computed properties, etc.
      return {
        // no need to return $a/$b/$styles, added to instance by vue-loader
      };
    }
  }
</script>

<style module>
  .wrapper {
    background: #000;
  }
</style>

<style module="$a">
  .wrapper {
    background: #ccc;
  }
</style>

<style module="$b">
  .wrapper {
    background: #fff;
  }
</style>

<script>
  export default {
    setup(props, context) {
      // Get undefined instead of { wrapper: <random-string> }
      return context.$style;
    }
  }
</script>

<style module>
  .wrapper {
    background: #000;
  }
</style>