code: def test_unpack_batch_sequence():
      batch = [[1, 2, 3], [2, 4, 6]]
      new_batch = SequencePackerUnpacker.unpack_batch(batch, {}, {})
      assert new_batch == {"_0": [1, 2], "_1": [2, 4], "_2": [3, 6]}
  
imports: from fastNLP.core.collators.packer_unpacker import MappingPackerUnpacker, NestedMappingPackerUnpacker, SequencePackerUnpacker
label_desc: Use image node_id 4 for calling a global function with example usage: test_unpack_batch_sequence() without return types