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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 _make_ip_subnet_lookup(vpc_info):
 """ Updates the vpc-info object with a lookup for IP -> subnet. """

    # We create a reverse lookup from the instances private IP addresses to the
    # subnets they are associated with. This is used later on in order to
    # determine whether routes should be set in an RT: Is the RT's subnet
    # associated with ANY of the IP addresses in the route spec? To make this
    # easy, we collect the IPs and subnets of all EC2 instances in the VPC.
    # Once we get a route spec, we create a list of subnets for only the
    # cluster nodes. The assumption is that not all EC2 instances in the VPC
    # necessarily belong to the cluster. We really want to narrow it down to
    # the cluster nodes only. See make_cluster_node_subnet_list().
    vpc_info['ip_subnet_lookup'] = {}
    for instance in vpc_info['instances']:
        for interface in instance.interfaces:
            subnet_id = interface.subnet_id
            for priv_addr in interface.private_ip_addresses:
                vpc_info['ip_subnet_lookup'][priv_addr.private_ip_address] = \
                                                                    subnet_id