code: def _roots_to_targets(self, build_graph, target_roots):
      
      with self._run_tracker.new_workunit(name='parse', labels=[WorkUnitLabel.SETUP]):
        return [
          build_graph.get_target(address)
          for address
          in build_graph.inject_roots_closure(target_roots, self._fail_fast)
        ]
docs: Populate the BuildGraph and target list from a set of input TargetRoots.