input: Write a python function to build a similar deep learning model using TensorFlow.
  assert isinstance(build_model(), tf.keras.Sequential)
  assert len(build_model().layers) == 9
  assert build_model().layers[0].filters == 32
output: def build_model():
      import tensorflow as tf
      from tensorflow.keras import layers
      
      model = tf.keras.Sequential([
          layers.Conv2D(32, (3, 3), activation='relu', input_shape=(28, 28, 1)),
          layers.MaxPooling2D((2, 2)),
          layers.Conv2D(64, (3, 3), activation='relu'),
          layers.MaxPooling2D((2, 2)),
          layers.Conv2D(64, (3, 3), activation='relu'),
          layers.Flatten(),
          layers.Dense(64, activation='relu'),
          layers.Dense(10, activation='softmax')
      ])
      
      return model