# === mod1.py ===
from mod2 import x

def z():
     y = x()
     print y.s
z()

# === mod2.py ===

from mod3 import w
from foo import bar

class x(object):
    def __init__(self):
        self.s = "HELLO"

bar.connect(x, w)

# === mod3.py ===
from mod2 import x
from foo import bar

class w(object):
    def __init__(self):
        self.z = "SDFD"

bar.connect(w, x)