code: def _updateExtraSelections(self):
          
          cursorColumnIndex = self.textCursor().positionInBlock()
  
          bracketSelections = self._bracketHighlighter.extraSelections(self,
                                                                       self.textCursor().block(),
                                                                       cursorColumnIndex)
  
          selections = self._currentLineExtraSelections() + \
                       self._rectangularSelection.selections() + \
                       bracketSelections + \
                       self._userExtraSelections
  
          self._nonVimExtraSelections = selections
  
          if self._vim is None:
              allSelections = selections
          else:
              allSelections = selections + self._vim.extraSelections()
  
          QPlainTextEdit.setExtraSelections(self, allSelections)
docs: Highlight current line