Tensorflow を用いて、Momentum 最適化を実装してください．( 慣性は 0.9 )
M_optimizer = ##########
1. tf.training.MomentumOptimizer(learning_rate=learning_rate, momentum=0.9)
2. tf.train.MomentumOptimizer(learning_rate=learning_rate, momentum=0.9)
3. tf.MomentumOptimizer(learning_rate=learning_rate, momentum=0.9)