Shrink list down to essentials

        :param shrink: List to shrink
        :type shrink: list
        :return: Shrunk list
        :rtype: list

def _shrink_list(self, shrink):
        """
        Shrink list down to essentials

        :param shrink: List to shrink
        :type shrink: list
        :return: Shrunk list
        :rtype: list
        """
        res = []

        if len(shrink) == 1:
            return self.shrink(shrink[0])
        else:
            for a in shrink:
                temp = self.shrink(a)

                if temp:
                    res.append(temp)
        return res