human
Solve the following python programming problem given the following code:
def _index(self, roots) : 
    'Index from the given roots into the storage provided by the base class.

    This is an additive operation: any existing connections involving these nodes are preserved.
    ' 
    all_addresses = set () 
    new_targets = list () 
    for (node, state) in self._graph.walk (roots = roots) : 
        if (type (state) is Throw) : 
            raise AddressLookupError ('Build graph construction failed for {}:
  {}'.format (state.subject, state.exc)) 
else : 
            if (type (state) is not Return) : 
                State.raise_unrecognized (state) 
if (node.product is not LegacyBuildGraphNode) : 
            continue 
if (type (node) is not SelectNode) : 
            continue 
(target_adaptor, dependency_addresses) = state.value 
        address = target_adaptor.address 
        all_addresses.add (address) 
        if (address not in self._target_by_address) : 
            new_targets.append (self._index_target (target_adaptor, dependency_addresses)) 
deps_to_inject = set () 
    addresses_to_inject = set () 
    def inject(target, dep_spec, is_dependency) : 
        address = Address.parse (dep_spec, relative_to = target.address.spec_path) 
        if (not any (((address == t.address) for t in target.dependencies))) : 
            addresses_to_inject.add (address) 
            if is_dependency : 
                deps_to_inject.add ((target.address, address)) 
for target in new_targets : 
        for spec in target.traversable_dependency_specs : 
            inject (target, spec, is_dependency = True) 
for spec in target.traversable_specs : 
            inject (target, spec, is_dependency = False) 
self.inject_addresses_closure (addresses_to_inject) 
    for (target_address, dep_address) in deps_to_inject : 
        self.inject_dependency (dependent = target_address, dependency = dep_address) 
return all_addresses 

    
    

    Fix the buggy line: raise AddressLookupError ('Build graph construction failed for {}:
  {}'.format (state.subject, state.exc))
assistant
#Here is Python code to fix the buggy line: raise AddressLookupError ('Build graph construction failed for {}:
.

raise AddressLookupError ('Build graph construction failed for {}:
  {}'.format (node.subject, state.exc))