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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 from_vhost(cls, vhost):
 """Retrieve paas instance id associated to a vhost."""

        result = Vhost().list()
        paas_hosts = {}
        for host in result:
            paas_hosts[host['name']] = host['paas_id']

        return paas_hosts.get(vhost)