code: function km(bundle) {
    assert.equal(typeof bundle, 'object')
  
    const handler = mr(bundle.toString())
  
    // koa middleware. Sets body to
    // be a css string.
    return function *koaMyth(next) {
      handler(this.req, this.res, function(err, body) {
        if (err) this.throw(err)
        this.response.body = body
        this.response.type = 'css'
      }.bind(this))
    }
  }
docs: koa myth @param  {String} bundle @return {GeneratorFunction}