code: def test_arrow_concat_empty():
      # Test empty.
      assert concat([]) == []
  
imports: import os
  import numpy
  import pandas
  import pyarrow
  import pytest
  import ray
  from ray.data._internal.arrow_ops.transform_pyarrow import concat, unify_schemas
  from ray.data.block import BlockAccessor
  from ray.data.extensions import ArrowTensorArray, ArrowTensorType, ArrowVariableShapedTensorType
label_desc: Use image node_id 1 for calling a global function with example usage: test_arrow_concat_empty() without return types