title: How to append rows to Gtk.ListStore?
body: <p>im trying to switch my application from python2.7 pyGTK to Python3 and pyGObject and having hard time with appending rows to my Gtk.ListStore :/</p>
  
  <p>This code:</p>
  
  <pre><code>#!/usr/bin/env python3
  
  from gi.repository import Gtk
  
  listStore = Gtk.ListStore(str)
  itr = Gtk.TreeIter()
  listStore.append(itr)
  listStore.set_value(itr, 0, 'Its working')
  </code></pre>
  
  <p>gives me always error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "./test.py", line 7, in &lt;module&gt;
      listStore.append(itr)
    File "/usr/lib/python3/dist-packages/gi/overrides/Gtk.py", line 1017, in append
      return self._do_insert(-1, row)
    File "/usr/lib/python3/dist-packages/gi/overrides/Gtk.py", line 1008, in _do_insert
      row, columns = self._convert_row(row)
    File "/usr/lib/python3/dist-packages/gi/overrides/Gtk.py", line 850, in _convert_row
      if len(row) != n_columns:
  TypeError: object of type 'TreeIter' has no len()
  </code></pre>
  
  <p>what is going on? How can I append new row into Gtk.ListStore?</p>