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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 metapolicy(request, permitted, domains=None):
 """ Serves a cross-domain policy which can allow other policies to exist on the same domain. Note that this view, if used, must be the master policy for the domain, and so must be served from the URL ``/crossdomain.xml`` on the domain: setting metapolicy information in other policy files is forbidden by the cross-domain policy specification. **Required arguments:** ``permitted`` A string indicating the extent to which other policies are permitted. A set of constants is available in ``flashpolicies.policies``, defining acceptable values for this argument. **Optional arguments:** ``domains`` A list of domains from which to allow access. Each value may be either a domain name (e.g., ``example.com``) or a wildcard (e.g., ``*.example.com``). Due to serious potential security issues, it is strongly recommended that you not use wildcard domain values. """

    if domains is None:
        domains = []
    policy = policies.Policy(*domains)
    policy.metapolicy(permitted)
    return serve(request, policy)