title: Pyqt - get CSV from model
body: <p>I have treeview based on proxymodel based on model.
  So I get a table, that can be filtered and sortered.</p>
  
  <p>I just want to export current view of this table to CSV file.
  Just what I see, export to a file or print.</p>
  
  <p>I suppose I have to use proxymodel for that, right?
  I cant find a method row or something like that.</p>
  
  <p>Really I have to use methods data(), rowCount() and collumnCount()?</p>
  
  <p>Thanks</p>