code: def _ExpandArtifactGroupSource(self, source, requested):
      
      artifact_list = []
      if "names" in source.attributes:
        artifact_list = source.attributes["names"]
      for artifact_name in artifact_list:
        if artifact_name in self.processed_artifacts:
          continue
        artifact_obj = artifact_registry.REGISTRY.GetArtifact(artifact_name)
        for expanded_artifact in self.Expand(artifact_obj, requested):
          yield expanded_artifact
docs: Recursively expands an artifact group source.