Args:
      output_path: Path to the directory to save the created model.
      tags: Set of strings that identifies the saved meta graph.
      signature_def_key: Name of the SignatureDef. Used to identify the
        SignatureDef within the meta graph.

    Returns:
      inputs: A mapping of input_key -> input_tensor (placeholder). The input
        key is "input_vocabs".

    seen_indices.insert(arg_index);
  }
  func->setAttr(
      kTfSavedModelExportedNamesAttr,
      mlir::ArrayAttr::get(
          context, {mlir::StringAttr::get(context, signature->signature_key)}));
}

// There are control nodes at each end of each control edge. For each of them,
// we store the source vertices of the incoming edges (if any) and the control