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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _cookie_attrs(self, cookies):
 """Return a list of cookie-attributes to be returned to server. The $Version attribute is also added when appropriate (currently only once per request). """

        # add cookies in order of most specific (ie. longest) path first
        cookies.sort(key=lambda a: len(a.path), reverse=True)

        version_set = False

        attrs = []
        for cookie in cookies:
            # set version of Cookie header
            # XXX
            # What should it be if multiple matching Set-Cookie headers have
            #  different versions themselves?
            # Answer: there is no answer; was supposed to be settled by
            #  RFC 2965 errata, but that may never appear...
            version = cookie.version
            if not version_set:
                version_set = True
                if version > 0:
                    attrs.append("$Version=%s" % version)

            # quote cookie value if necessary
            # (not for Netscape protocol, which already has any quotes
            #  intact, due to the poorly-specified Netscape Cookie: syntax)
            if ((cookie.value is not None) and
                self.non_word_re.search(cookie.value) and version > 0):
                value = self.quote_re.sub(r"\\\1", cookie.value)
            else:
                value = cookie.value

            # add cookie-attributes to be returned in Cookie header
            if cookie.value is None:
                attrs.append(cookie.name)
            else:
                attrs.append("%s=%s" % (cookie.name, value))
            if version > 0:
                if cookie.path_specified:
                    attrs.append('$Path="%s"' % cookie.path)
                if cookie.domain.startswith("."):
                    domain = cookie.domain
                    if (not cookie.domain_initial_dot and
                        domain.startswith(".")):
                        domain = domain[1:]
                    attrs.append('$Domain="%s"' % domain)
                if cookie.port is not None:
                    p = "$Port"
                    if cookie.port_specified:
                        p = p + ('="%s"' % cookie.port)
                    attrs.append(p)

        return attrs