code: def get_learning_rate(self, iter):
      return self.init_lr * (self.gamma ** (iter // self.iter_interval))
  
file_path: nnabla/python/test/utils/learning_rate_scheduler/test_exponential_scheduler.py
imports: import pytest
  from learning_rate_scheduler_test_utils import scheduler_tester
  import nnabla.utils.learning_rate_scheduler
label_desc: Use image node_id 2 for calling the RefExponential obj's underlying member method code with example usage: obj.get_learning_rate(iter) and returns: unknown