code: def extraSelections(self, qpart, block, columnIndex):
          
          blockText = block.text()
  
          if columnIndex < len(blockText) and \
               blockText[columnIndex] in self._ALL_BRACKETS and \
               qpart.isCode(block, columnIndex):
              return self._highlightBracket(blockText[columnIndex], qpart, block, columnIndex)
          elif columnIndex > 0 and \
             blockText[columnIndex - 1] in self._ALL_BRACKETS and \
             qpart.isCode(block, columnIndex - 1):
              return self._highlightBracket(blockText[columnIndex - 1], qpart, block, columnIndex - 1)
          else:
              self.currentMatchedBrackets = None
              return []
docs: List of QTextEdit.ExtraSelection's, which highlighte brackets