Core_kernel Uuid module not found

I see a Uuid module in the docs:

When I try to use it in utop, I get an error:

# #require "core_kernel";;
# open Core_kernel;;
# Uuid.create ();;
Line 1, characters 0-11:
Error: Unbound module Uuid

Any suggestions?

The Uuid related things are published in a library core_kernel.uuid. You need to load it via:
#require "core_kernel.uuid"