title: cant install Adam from keras.optimizer
body: <p>Was working on google colab yesterday and everything works fine. but now I got a problem when trying to import Adam.</p>
  <p>this is what I try to import</p>
  <pre><code>from keras.optimizers import Adam, SGD, RMSprop
  </code></pre>
  <p>this is what I got</p>
  <pre><code>ImportError                               Traceback (most recent call last)
  &lt;ipython-input-1-36a1fe725448&gt; in &lt;module&gt;()
       30 from keras.layers import GlobalAveragePooling2D
       31 from keras.layers import BatchNormalization, Activation, MaxPooling2D
  ---&gt; 32 from keras.optimizers import Adam, SGD, RMSprop
  
  ImportError: cannot import name 'Adam' from 'keras.optimizers' (/usr/local/lib/python3.7/dist-packages/keras/optimizers.py)
  
  ---------------------------------------------------------------------------
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  </code></pre>