Highlights given text.

        :param text: Text.
        :type text: QString
        :param start: Text start index.
        :type start: int
        :param end: Text end index.
        :type end: int
        :return: Method success.
        :rtype: bool

def highlight_text(self, text, start, end):
        """
        Highlights given text.

        :param text: Text.
        :type text: QString
        :param start: Text start index.
        :type start: int
        :param end: Text end index.
        :type end: int
        :return: Method success.
        :rtype: bool
        """

        for rule in self.__rules:
            index = rule.pattern.indexIn(text, start)
            while index >= start and index < end:
                length = rule.pattern.matchedLength()
                format = self.formats.get_format(rule.name) or self.formats.get_format("default")
                self.setFormat(index, min(length, end - index), format)
                index = rule.pattern.indexIn(text, index + length)
        return True