title: Undo text entry in Jupyter Notebook under Win7
body: <p>I was surprised I did not find an answer to this question on Jupyter Notebook under Win7 here or on the web.</p>
  
  <p>I just overwrote by mistake a larger part of a call block, but not all. Autosave dates back some previous changes that I do not want to revert. Where is the undo function for text entries in Jupyter Notebook?</p>