custom-initialize-setcustom-initialize-set is a compiled Lisp function in `
custom.el'. (custom-initialize-set SYMBOL EXP) Initialize SYMBOL based on EXP. If the symbol doesn't have a default binding already, then set it using its `:set' function (or `set-default' if it has none). The value is either the value in the symbol's `saved-value' property, if any, or the value of EXP.