Returns the result filters

        :rtype: str or None

def get_filters(self):
        """ Returns the result filters

        :rtype: str or None
        """
        if self._filters:
            filters_list = self._filters
            if isinstance(filters_list[-1], Enum):
                filters_list = filters_list[:-1]
            return ' '.join(
                [fs.value if isinstance(fs, Enum) else fs[1] for fs in
                 filters_list]).strip()
        else:
            return None