code: function dflowFun () {
      var gotReturn = false
      var returnValue
      var outs = {}
  
      // Inject run-time builtin tasks.
  
      funcs['this'] = function () { return dflowFun }
      funcs['this.graph'] = function () { return graph }
      injectArguments(funcs, task, arguments)
  
      /**
       * Execute task.
       */
  
      function run (taskKey) {
        var args = inputArgs(outs, pipe, taskKey)
        var taskName = task[taskKey]
        var f = funcs[taskName]
  
        // Behave like a JavaScript function:
        // if found a return, skip all other tasks.
  
        if (gotReturn) return
  
        if ((taskName === 'return') && (!gotReturn)) {
          returnValue = args[0]
          gotReturn = true
          return
        }
  
        // If task is not defined at run time, throw an error.
  
        if (no(f)) {
          var taskNotFound = new Error('Task not found: ' + taskName + ' [' + taskKey + '] ')
          taskNotFound.taskKey = taskKey
          taskNotFound.taskName = taskName
        }
  
        // Try to execute task.
  
        try {
          outs[taskKey] = f.apply(null, args)
        } catch (err) {
          // Enrich error with useful dflow task info.
          err.taskName = taskName
          err.taskKey = taskKey
  
          throw err
        }
      }
  
      // Run every graph task, sorted by level.
  
      Object.keys(task)
        .filter(comments)
        .sort(byLevel)
        .forEach(run)
  
      return returnValue
    }
docs: Here we are, this is the ❤ of dflow.