code: function checkTaskIsCompiled (taskKey) {
      var taskName = task[taskKey]
  
      // Ignore tasks injected at run time.
      if (reservedKeys.indexOf(taskName) > -1) return
  
      var msg = 'Task not compiled: ' + taskName + ' [' + taskKey + ']'
  
      // Check subgraphs.
      if (regexSubgraph.test(taskName)) {
        var subgraphKey = taskName.substring(1)
  
        if (no(graph.func[subgraphKey])) {
          var subgraphNotFound = new Error(msg)
          subgraphNotFound.taskKey = taskKey
          subgraphNotFound.taskName = taskName
          throw subgraphNotFound
        } else return
      }
  
      // Skip dflow DSL.
      if (isDflowDSL(taskName)) return
  
      // Skip globals.
      if (walkGlobal(taskName)) return
  
      if (no(funcs[taskName])) {
        var subgraphNotCompiled = new Error(msg)
        subgraphNotCompiled.taskKey = taskKey
        subgraphNotCompiled.taskName = taskName
        throw subgraphNotCompiled
      }
    }
docs: Throw if a task is not compiled.