code: def test_arrow_concat_single_block():
      # Test single block:
      t = pa.table({"a": [1, 2]})
      out = concat([t])
      assert len(out) == 2
      assert out == t
  
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 2 for calling a global function with example usage: test_arrow_concat_single_block() without return types