def connect_generations(self):
<EOL>for src in self.sources.values():<EOL><INDENT>for _child in src.imports:<EOL><INDENT>if _child in self.sources:<EOL><INDENT>child = self.sources[_child]<EOL>child.imported_by.add(src.name)<EOL><DEDENT><DEDENT><DEDENT>
Traverse depth-first adding imported_by.