title: module 'keras.backend' has no attribute 'symbolic'
body: <p>I am using Google Colab and installed the following libraies:</p>
  <pre><code>!pip3 install tensorflow==2.2
  !pip3 install keras==2.3.1
  !pip install keras_adamw
  </code></pre>
  <p>When I import &quot;keras_adamw&quot; I get this error:</p>
  <pre><code>---------------------------------------------------------------------------
  AttributeError                            Traceback (most recent call last)
  &lt;ipython-input-12-f0562343d039&gt; in &lt;module&gt;()
  ----&gt; 1 from keras_adamw import AdamW
  /usr/local/lib/python3.7/dist-packages/keras_adamw/__init__.py in &lt;module&gt;()
       22 else:
       23     if TF_2 or KERAS_23:
  ---&gt; 24         from .optimizers import AdamW, NadamW, SGDW
       25     else:
       26         from .optimizers_225 import AdamW, NadamW, SGDW
  
  /usr/local/lib/python3.7/dist-packages/keras_adamw/optimizers.py in &lt;module&gt;()
       12
       13
  ---&gt; 14 class AdamW(Optimizer):
       15     &quot;&quot;&quot;AdamW optimizer.
       16     Default parameters follow those provided in the original paper.
  /usr/local/lib/python3.7/dist-packages/keras_adamw/optimizers.py in AdamW()
       113 
       114     @interfaces.legacy_get_updates_support
  --&gt;  115     @K.symbolic
       116     def get_updates(self, loss, params):
       117         grads = self.get_gradients(loss, params)
  
  AttributeError: module 'keras.backend' has no attribute 'symbolic'
  </code></pre>
  <p>I tried to search but I did not find any posts with similar error.</p>