Does class definition in constructor of another python class define memory leak?

Not sure if I'm doing something clearly wrong, but the following Python code seems to be leaking in memory:

class A(object):
    def __init__(self):
        class B(object):
            pass

for i in range(0, 100):
    a = A()
a = None

      

        
        
        
      

    

From my understanding of Python garbage collection, all objects created should be garbage collected at the end of this sample program. However, there are objects on the heap on the left floating around. The number of objects grows with the number of cycles, but it does so sublinearly.

If I comment out the inner class B

it no longer leaks.

This dummy example has been tested using guppy

both Python 2.7.12. I have not tested it with Python 3, but we observed the same effects as our software, which initially gave an error under Python 2 and 3.