Well, because it's a definition, not an example. You'd need lots of examples to replace a definition, think of "expr" (expression). An expression can be a lot, it may contain operators, paranthesis and what not.
So the definition of
local id := expr
ranges from the simple example
local a = true
via
local somerandomvariablename = { "foobar":[0,1,2,3] }
to
local WhatTheHeckIsHetThinkingAboutVariableNames = (sin(5)*("0.4565".tofloat())/somefunction(this)?1:anotherweirdfunc.bindenv(a).call({a=a,"b":"I'm a nutter",[null]},true) || (this()<-@"haha,hope that 'this' is no class!")
or even stranger expressions. You get the idea I think :)