title: Model Checkpoint doesn't create a directory
body: <p>I was learning about model saving in Keras, and it seems like my model checkpoint object doesn't create the specified directory. Here is the code:</p>
  
  <pre><code>from tensorflow.keras.callbacks import ModelCheckpoint
  checkpoint_5000_path = \
      'model_checkpoints_5000/checkpoint_{epoch:02d}_{batch:04d}'
  checkpoint_5000 = ModelCheckpoint(filepath=checkpoint_5000_path,
                                    save_freq=5000,
                                    save_weights_only=True,
                                    verbose=2)
  model = get_new_model()
  model.fit(x_train,y_train,epochs=10,validation_split=0.15,callbacks=[checkpoint_5000],verbose=2)
  </code></pre>
  
  <p>When I try to access the directory,</p>
  
  <pre><code>! ls -lh model_checkpoints_5000
  </code></pre>
  
  <p>this error shows up.</p>
  
  <pre><code>ls: cannot access 'model_checkpoints_5000': No such file or directory
  </code></pre>
  
  <p>What could be the reason for this?
  Btw I am not doing this on my local machine. I use Google Colab.</p>