docs: def completerTree( self ):
          """
          Returns the completion tree for this instance.
          
          :return     <QTreeWidget>
          """
          if not self._completerTree:
              self._completerTree = QTreeWidget(self)
              self._completerTree.setWindowFlags(Qt.Popup)
              self._completerTree.setAlternatingRowColors( True )
              self._completerTree.installEventFilter(self)
              self._completerTree.itemClicked.connect( self.acceptCompletion )
              self._completerTree.setRootIsDecorated(False)
              self._completerTree.header().hide()
              
          return self._completerTree