Returns Category object by its alias.

        :param str alias:
        :rtype: Category|None
        :return: category object

def get_category_by_alias(self, alias):
        """Returns Category object by its alias.

        :param str alias:
        :rtype: Category|None
        :return: category object
        """
        self._cache_init()
        return self._cache_get_entry(self.CACHE_NAME_ALIASES, alias, None)