title: How to protect a column in excel against changes using openpyxl?
body: <p>I'd like to lock out some of the columns in the  for changes. To do that, I first locked out the entire file.</p>
  
  <pre><code>ws = wb["RFI"]
  ws.protection.sheet = True
  </code></pre>
  
  <p>But then I try lock some of columns</p>
  
  <pre><code>for col in ['U', 'V', 'W', 'X', 'Y', 'Z', 'AA', 'AB', 'AC', 'AD']:
      ws[col].protection = Protection(locked=False)
  </code></pre>
  
  <p>I got</p>
  
  <pre><code>AttributeError: 'tuple' object has no attribute 'protection'
  </code></pre>