Gulp 4 is not working

`After I upgraded to gulp 4. I’m seeing the following error’

AssertionError [ERR_ASSERTION]: Task function must be specified
at Gulp.set [as _setTask] (/Users/manivannant/newPrj/ReachClient/Web/node_modules/undertaker/lib/set-task.js:10:3)
at Gulp.task (/Users/manivannant/newPrj/ReachClient/Web/node_modules/undertaker/lib/task.js:13:8)
at module.exports (/Users/manivannant/newPrj/ReachClient/Web/gulp/tasks/adkdoc.js:51:10)
at /Users/manivannant/newPrj/ReachClient/Web/gulpfile.js:105:33
at ()
at Object. (/Users/manivannant/newPrj/ReachClient/Web/gulpfile.js:97:44)
at Module._compile (internal/modules/cjs/loader.js:778:30)
at Object.Module._extensions…js (internal/modules/cjs/loader.js:789:10)
at Module.load (internal/modules/cjs/loader.js:653:32)
at tryModuleLoad (internal/modules/cjs/loader.js:593:12)

As per the information available from the forum, I did updated some of the task with gulp.series() task.
But still the issue is not resolved. I believe the following line causes the issue.

require(’./gulp/tasks/’ + file)(gulp, argv);

Any help appreciated```

Welcome, manivannan.

Please indicate which lesson from the curriculum this is from, and, if possible, do this by linking to the lesson. This will encourage your question to be answered.

Happy coding.