docs: function use(plugin) {
    var self = this
    var pipeline = self.pipeline
    var duplicate = false
  
    if (plugin && plugin.pluginId) {
      duplicate = self.plugins.some(matches)
    }
  
    if (!duplicate && self.plugins.indexOf(plugin) !== -1) {
      duplicate = true
    }
  
    if (!duplicate) {
      self.plugins.push(plugin)
      pipeline.use(plugin)
    }
  
    return self
  
    function matches(fn) {
      return fn.pluginId === plugin.pluginId
    }
  }