Suppose I want a function that runs some setup code before it runs the first time. Maybe I’m using dplyr but I haven’t properly declared all of my dplyr calls in my function, so I want to run library(dplyr) before the actual function is run. Or maybe I want to install a package if it isn’t already installed, or restore a renv file, or any other setup process. I only want this special code to run the first time my function is called.