| 1234567891011121314151617181920212223242526272829303132333435 | let Prefixer = require('./prefixer')class AtRule extends Prefixer {  /**   * Clone and add prefixes for at-rule   */  add(rule, prefix) {    let prefixed = prefix + rule.name    let already = rule.parent.some(      i => i.name === prefixed && i.params === rule.params    )    if (already) {      return undefined    }    let cloned = this.clone(rule, { name: prefixed })    return rule.parent.insertBefore(rule, cloned)  }  /**   * Clone node with prefixes   */  process(node) {    let parent = this.parentPrefix(node)    for (let prefix of this.prefixes) {      if (!parent || parent === prefix) {        this.add(node, prefix)      }    }  }}module.exports = AtRule
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