title: Notebook Validation Failed
body: <p>While running jupyter notebook I get this error. Any idea?</p>
  
  <pre><code>An invalid notebook may not function properly. The validation error was:
  Notebook validation failed: ['outputPrepend', 'outputPrepend', 'outputPrepend', 'outputPrepend', 'outputPrepend'] has non-unique elements:
  [
   "outputPrepend",
   "outputPrepend",
   "outputPrepend",
   "outputPrepend",
   "outputPrepend"
  ]
  </code></pre>