code: def duplicate_lines(self):
          
  
          cursor = self.textCursor()
          self.__select_text_under_cursor_blocks(cursor)
          text = cursor.selectedText()
  
          cursor.setPosition(cursor.block().next().position())
          cursor.position() == cursor.document().firstBlock().position() and cursor.setPosition(
              cursor.document().lastBlock().position())
  
          start_position = cursor.position()
          cursor.insertText(text)
          end_position = cursor.position()
          cursor.insertText(QChar(QChar.ParagraphSeparator))
  
          cursor.setPosition(start_position, QTextCursor.MoveAnchor)
          cursor.setPosition(end_position, QTextCursor.KeepAnchor)
          self.setTextCursor(cursor)
  
          return True
docs: Duplicates the document lines under cursor.
  
          :return: Method success.
          :rtype: bool