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