Questions about these lines of code

[LiuYinCarl]

In function make_frame, I dont't understand these lines of code's effect.

    def make_frame(self, code, callargs={}, f_globals=None, f_locals=None):
        log.info("make_frame: code=%r, callargs=%s" % (code, repper(callargs)))
        # if f_globals is not None:
        #     f_globals = f_globals
        #     if f_locals is None:
        #         f_locals = f_globals
        # Can the above lines be modified like this
        if f_globals is not None and f_locals is None:
                f_locals = f_globals

        elif self.frames:
            f_globals = self.frame.f_globals
            f_locals = {}
        else:
            f_globals = f_locals = {
                '__builtins__': __builtins__,
                '__name__': '__main__',
                '__doc__': None,
                '__package__': None,
            }
        f_locals.update(callargs)
        frame = Frame(code, f_globals, f_locals, self.frame)
        return frame