code: def test_learning_rate_in_history(self):
      lr_scheduler = callbacks.LearningRateScheduler(
          lambda step, lr: 0.5
      )
  
      history = self.model.fit(
          self.x_train,
          self.y_train,
          callbacks=[lr_scheduler],
          epochs=1,
      )
  
      self.assertTrue("learning_rate" in history.history)
      self.assertEqual(type(history.history["learning_rate"][0]), float)
      self.assertEqual(history.history["learning_rate"][0], 0.5)
  
file_path: keras/keras/callbacks/learning_rate_scheduler_test.py
imports: import pytest
  from keras import callbacks
  from keras import layers
  from keras import optimizers
  from keras import testing
  from keras.models import Sequential
  from keras.testing import test_utils
  from keras.utils import io_utils
  from keras.utils import numerical_utils
label_desc: Use image node_id 6 for calling the LearningRateSchedulerTest obj's underlying member method code with example usage: obj.test_learning_rate_in_history() without return types