Leader by default is \ (but I've mapped it to , with let mapleader = ","). Similarly, using imap you can map some key sequence in insert mode (but then, if it is 2 key sequence, it probably will override some default behaviour).
Aside: when this function was executed (Vim 8.1) in my terminal, the Vim screen was obfuscated (mostly "blanked;" i.e., the text was there but not visible). The :redraw! command (see https://stackoverflow.com/a/1117742/1904943) redraws the screen.