'Returns the model matching the given app_label and case-insensitive
model_name.
Returns None if no model is found.'

def get_model(self, app_label, model_name, seed_cache=True, only_installed=True):

    if seed_cache:
        self._populate()
    if (only_installed and (app_label not in self.app_labels)):
        return None
    return self.app_models.get(app_label, SortedDict()).get(model_name.lower())
