human
Solve the following python programming problem given the following code:
def calculate_filters(choice_type, choice_pk) : 
    "
    Write three functions that given a list of present primary keys
    ('present_pks') that are in the UI will remove the correct pk's and
    return a list of raised objects.

    filter_network will return a list of Networks
    filter_site will return a list of Sites
    filter_vlan will return a list of Vlans

    The 'present_pks' value is a list of integers that represent primary
    keys of the type of objects the function returns.
    " 
    if (choice_type == 'network') : 
        network = get_object_or_404 (Network, pk = choice_pk) 
        def filter_network(present_pks) : 
            return [network] 
def filter_site(present_pks) : 
            return ([network.site] if network.site else []) 
def filter_vlan(present_pks) : 
            return ([network.vlan] if network.vlan else []) 
else : 
        if (choice_type == 'site') : 
            def filter_network(present_pks) : 
                "
            Remove any present network pk's that aren't in the network
            " 
                site_network_pks = get_object_or_404 (Site, pk = choice_pk).network_set.filter (UN).values_list ('pk', flat = True) 
                net_pks = set (present_pks).intersection (set (site_network_pks)) 
                return pks_to_objs (net_pks, Network) 
def filter_site(present_pks) : 
                return [get_object_or_404 (Site, pk = choice_pk)] 
def filter_vlan(present_pks) : 
                vlans = pks_to_objs (present_pks, Vlan) 
                def is_in_site(vlan) : 
                    return vlan.network_set.filter (site__pk = choice_pk).filter (UN).exists () 
return filter (is_in_site, vlans) 
else : 
            if (choice_type == 'vlan') : 
                vlan = get_object_or_404 (Vlan, pk = choice_pk) 
                def filter_network(present_pks) : 
                    net_pks = vlan.network_set.filter (UN).values_list ('pk', flat = True) 
                    net_pks = set (present_pks).intersection (set (net_pks)) 
              ...

    
    

    Fix the buggy line: return (filter_network, filter_site, choice_pk)
assistant
#Here is Python program to fix the buggy line: return (filter_network, filter_site, choice_pk)
.

return (filter_network, filter_site, def filter_vlan()