title: pandas: TypeError: unhashable type: 'list'
body: <p>I have the following <code>df</code>:</p>
  <pre><code>df = pd.DataFrame(
      [
          [[&quot;John Muller&quot;], &quot;person&quot;, [8866155845]],
          [[&quot;Innovation Division&quot;], &quot;company&quot;, np.nan],
          [[&quot;Carol Sway&quot;], &quot;person&quot;, [8866155845]],
      ],
      columns=[&quot;name&quot;, &quot;kind&quot;, &quot;phone&quot;],
  )
  
  # Out:
  #                     name     kind         phone
  # 0          [John Muller]   person  [8866155845]
  # 1  [Innovation Division]  company           NaN
  # 2           [Carol Sway]   person  [8866155845]
  </code></pre>
  <p>and I want to find duplicates of a phone number. But the objects in <code>df</code> are lists, so using:</p>
  <pre><code>df.duplicated('phone') 
  </code></pre>
  <p>will generate the error:</p>
  <pre><code>TypeError: unhashable type: 'list'
  </code></pre>