Checking if a Python function referenced anything out-of-scope

I'm exploring what's possible to do in Python and recently came across this question: after running a function, is it possible to programmatically determine whether it has referenced anything out-of-scope? For example:

import module1

y = 1

def foo1(x):
    return y + x  # yes - it has referenced 'y' which is out of foo1 scope

def foo2(x):
    return module1.function1(x)  # yes - it has referenced 'module1' which is out of foo2 scope

def foo3(x):
    return x*x  # no - it has only referenced 'x' which is an input to foo3, so the code executed within the scope of foo3

Are there some reflection / analysis tools for this? Maybe this could be achieved with the 'trace' module somehow?