If you want to enable your Joblet to call any function in a routine or custom routine jar, you need to set up code dependencies, namely routine or custom routine jar dependencies, on the Joblet.
Note that you can set up custom routine jar dependencies on a Joblet only if you have installed the R2021-03 Studio monthly update or a later one provided by Talend.
You can set up code dependencies on a Joblet in the same way as setting up code dependencies on a Job. For more information, see Setting up code dependencies on a Job.