Track required modules, either explicitly imported or providing dependencies, as
opposed to those providing objects defined elsewhere.
1deff(x): 2defg(y): 3while1: 4defh(z): 5returnx,y,z,a 6a=4# not available for h, available in Python 7returnh 8returng 9 10result=f(1)(2)(3) 11assertresult==(1,2,3,4)