code: def convert_indentation_to_tabs(self):
          
  
          cursor = self.textCursor()
  
          block = self.document().findBlockByLineNumber(0)
          while block.isValid():
              cursor.setPosition(block.position())
              search = re.match(r"^ +", block.text())
              if search:
                  cursor.movePosition(QTextCursor.StartOfBlock, QTextCursor.MoveAnchor)
                  searchLength = len(search.group(0))
                  foundations.common.repeat(
                      lambda: cursor.movePosition(QTextCursor.Right, QTextCursor.KeepAnchor), searchLength)
                  cursor.insertText(self.__indent_marker * (searchLength / self.__indent_width))
              block = block.next()
          return True
docs: Converts document indentation to tabs.
  
          :return: Method success.
          :rtype: bool