title: Keras ValueError: Input 0 is incompatible with layer conv2d_1: expected ndim=4, found ndim=5
body: <p>I have checked all the solutions, but still, I am facing the same error. My training images shape is <code>(26721, 32, 32, 1)</code>, which I believe it is 4 dimension, but I don't know why error shows it is 5 dimension. </p>
  
  <pre><code> model = Sequential()
  
   model.add(Convolution2D(16, 5, 5, border_mode='same', input_shape= input_shape ))
  </code></pre>
  
  <p>So this is how I am defining <code>model.fit_generator</code> </p>
  
  <pre><code>model.fit_generator(train_dataset, train_labels, nb_epoch=epochs, verbose=1,validation_data=(valid_dataset, valid_labels), nb_val_samples=valid_dataset.shape[0],callbacks=model_callbacks)
  </code></pre>