a.py

class Sess:
    def __init__(self, foo):
        self.foo = foo
        print("init Sess")

class Lock:
    def __init__(self):
        print("init Lock")

class AppC:
    def __init__(self):
        self.apps = dict()
        print("init AppC")

class MemSess(Sess, Lock, AppC):
    def __init__(self, *args, **kw):
        super().__init__(*args, **kw)
        print("init MemSess")

m = MemSess("bar")
print(m.apps)