def __init__(self, package, version):
        """Construct a new requirement.

        :param package: the package name.
        :param version: a semver compatible version specification.
        """
        self.package = package
        self.version = version
        if self.version and not re.match(r"[<=>~]", version[:2]):
            self.version = "=={}".format(self.version)
def _getQUICHeader(self, count):
        if type(count) is not hex:
            try:
                count_id = chr(count)
            except:
                sys.stderr.write("Count must be int or hex.\n")
                return 1
        else:
            count_id = count

        if count > self.max_packets:
            sys.stderr.write("[-]\tCount must be maximum of 255.\n")
            return 1

        header = "\x0c"                     # Public Flags
        header += self.sequence             # Adding CID
        header += count_id                  # Packet Count
        return header