The following code<<
-- Enforce modname:cooldown_name naming convention
local current_modname = minetest.get_current_modname()
local expected_prefix = current_modname .. ":"
if name:sub(1, #expected_prefix) ~= expected_prefix then
	error("Name " .. name .. " does not follow naming conventions: " .. "\"" .. expected_prefix .. "\" required")
end
-- Enforce that the name only contains letters, numbers and underscores.
local subname = name:sub(#expected_prefix+1)
if subname:find("[^%w_]") then
	error("Name " .. name .. " does not follow naming conventions: " .. "contains unallowed characters")
end
if adjustable_cooldowns.cooldowns[current_modname] == nil then
	adjustable_cooldowns.cooldowns[current_modname] = {}
end
>> has been modified from the following code<<
local function check_modname_prefix(name)
	if name:sub(1,1) == ":" then
		-- If the name starts with a colon, we can skip the modname prefix
		-- mechanism.
		return name:sub(2)
	else
		-- Enforce that the name starts with the correct mod name.
		local expected_prefix = core.get_current_modname() .. ":"
		if name:sub(1, #expected_prefix) ~= expected_prefix then
			error("Name " .. name .. " does not follow naming conventions: " ..
				"\"" .. expected_prefix .. "\" or \":\" prefix required")
		end

		-- Enforce that the name only contains letters, numbers and underscores.
		local subname = name:sub(#expected_prefix+1)
		if subname:find("[^%w_]") then
			error("Name " .. name .. " does not follow naming conventions: " ..
				"contains unallowed characters")
		end

		return name
	end
end
>> found in the register.lua in the base minetest game. [don't currently know the original author(s)]