code: def test_pack_batch_nested_mapping():
      batch = {
          "a": [[1, 2], [3]],
          "b": [1, 2],
          ("c", "c", "c"): [1, 2],
          ("c", "c", "d"): [[1, 1], [2, 2]],
          ("c", "d"): [[1], [2, 2]],
      }
      new_batch = NestedMappingPackerUnpacker.pack_batch(batch)
      assert new_batch == {
          "a": [[1, 2], [3]],
          "b": [1, 2],
          "c": {
              "c": {"c": [1, 2], "d": [[1, 1], [2, 2]]},
              "d": [[1], [2, 2]],
          },
      }
  
imports: from fastNLP.core.collators.packer_unpacker import MappingPackerUnpacker, NestedMappingPackerUnpacker, SequencePackerUnpacker
label_desc: Use image node_id 3 for calling a global function with example usage: test_pack_batch_nested_mapping() without return types