Finds all subclasses of `clazz` in `module`, returns a list.

find_subclasses.py

def find_subclasses(module, clazz):
    """
    Finds all subclasses of `clazz` in `module`, returns a list.
    Source: http://stackoverflow.com/a/408465
    """
    return [
        cls for name, cls in inspect.getmembers(module)
            if inspect.isclass(cls) and issubclass(cls, clazz)
    ]