Tuner object for Keras tuner in Google Collab throws NotImplementedError

I am trying to do Hyperparameter tuning through Keras Tuner in Google Collab with the Following code. While creating tuner object it gives error as follows:

import keras_tuner as kt
def build_model(hp):
  model = Sequential()
  model.add(Dense(32, activation = 'relu', input_dim = 8))
  model.add(Dense(1, activation = 'sigmoid'))
  optimizer = hp.choice('optimizer', values = ['adam', 'sgd', 'rmsprop', 'adadelta'])
  model.compile(optimizer = optimizer, loss = 'binary_crossentropy', metrics='accuracy')
  return model
tuner = kt.RandomSearch(build_model, objective = 'val_accuracy', max_trials= 5)

NotImplementedError                       Traceback (most recent call last)
/usr/local/lib/python3.7/dist-packages/keras_tuner/engine/base_tuner.py in _populate_initial_space(self)
    127         try:
--> 128             self.hypermodel.declare_hyperparameters(hp)
    129         except NotImplementedError:

6 frames
NotImplementedError: 

During handling of the above exception, another exception occurred:

AttributeError                            Traceback (most recent call last)
<ipython-input-49-9df1bab4dd0e> in build_model(hp)
      4   model.add(Dense(32, activation = 'relu', input_dim = 8))
      5   model.add(Dense(1, activation = 'sigmoid'))
----> 6   optimizer = hp.choice('optimizer', values = ['adam', 'sgd', 'rmsprop', 'adadelta'])
      7   model.compile(optimizer = optimizer, loss = 'binary_crossentropy', metrics='accuracy')
      8   return model

AttributeError: 'HyperParameters' object has no attribute 'choice'