title: issue in nested dictionary when try to iterate through value
body: <p>Why below code giving me an error?</p>
  <pre><code>nested_dict = {'first':{'a':1},'second':{'b':2}}
  {i for i in nested_dict.values()}
  </code></pre>
  <p>error:</p>
  <pre><code>---------------------------------------------------------------------------
  TypeError                                 Traceback (most recent call last)
  C:\Users\ABHINA~1\AppData\Local\Temp/ipykernel_12056/1167728052.py in &lt;module&gt;
  ----&gt; 1 {i for i in nested_dict.values()}
  
  C:\Users\ABHINA~1\AppData\Local\Temp/ipykernel_12056/1167728052.py in &lt;setcomp&gt;(.0)
  ----&gt; 1 {i for i in nested_dict.values()}
  
  TypeError: unhashable type: 'dict'
  </code></pre>