def get_regex_strings(self, regular_expressions):
        """
        Return all target strings matched the regex

        :param regular_expressions: the python regex
        :type regular_expressions: string

        :rtype: a list of strings matching the regex expression
        """
        str_list = []
        if regular_expressions.count is None:
            return None
        for i in self.get_strings():
            if re.match(regular_expressions, i):
                str_list.append(i)
        return str_list