post_init and other hooks are coded as instance methods but aren't actually instance methods

[pcraciunoiu]

This leads to a bit of weirdness where you have to call self.post_init() and pass self as the first argument.

Per Andy's comments, here is how it currently works:

>>> class a(object):
...   pass
...⋅
>>> def foo(self):
...   self.a = 5
...⋅
>>> b = a()
>>> b.hello = foo
>>> b.hello()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: foo() takes exactly 1 argument (0 given)
>>> b.hello(b)
>>> b.a
5

And here is how it could work:

>>> class a(object):
...   pass
...⋅
>>> def foo(self):
...   self.a = 5
...⋅
>>> b = a()
>>> import types
>>> b.hello = types.MethodType(foo, b)
>>> b.hello()
>>> b.a
5