'Get the classes from a module that match the type we want.'

def _get_classes_from_module(self, module_name):

    classes = []
    module = importutils.import_module(module_name)
    for obj_name in dir(module):
        if obj_name.startswith('_'):
            continue
        itm = getattr(module, obj_name)
        if self._is_correct_class(itm):
            classes.append(itm)
    return classes
