class results in org mode with python

I am having difficulties in using python classes in org-mode.
Here is a simple illustration of an org mode file:

First let's define a class

#+BEGIN_SRC python :session :exports code
class The_class():
    def __init__(self, a):
        self.a = a

    def add_me(self):
        return self.a + self.a

    def sqr_me(self):
        return self.a**2

#+END_SRC

Then check the class:

#+BEGIN_SRC python :session :exports both :results output 
itm = The_class(3)
print('value of itm.a: {0}'.format(itm.a))
print('attributes: {0}'.format(itm.__dict__))
print('methods of itm: {0}'.format(dir(itm)))
#+END_SRC

And make calculation:

#+BEGIN_SRC python :session :exports both :results output
print(itm.add_me()) 
print(itm.sqr_me())
#+END_SRC

The second block code correctly identifies the attributes, however, it fails to recognize either self.add_me() or self.sqr_me() methods in the dir(self). As a consequence, when upon calling itm.add_me(), it gives me a: for example:

#+RESULTS: 
: Traceback (most recent call last): 
:   File "<stdin>", line 1, in <module> 
:   File "/var/folders/l7/3vzbfyz93z1fz31m3m6srjcm0000gn/T/babel-18019W4Z/python-1801928I", line 1, in <module> 
:     print(itm.add_me())  
: AttributeError: 'The_class' object has no attribute 'add_me' :

Any ideas what is going on?

The problem comes from the newlines. Just remove them.

#+BEGIN_SRC python :session :exports code
class The_class():
    def __init__(self, a):
        self.a = a
    def add_me(self):
        return self.a + self.a    
    def sqr_me(self):
        return self.a**2

#+END_SRC