code: def test_hash_agg_empty(unary_agg_func_fixture):
      arr1 = pa.array([], pa.float64())
      arr2 = pa.array([], pa.int32())
      table = pa.table([arr2, arr1], names=["id", "value"])
  
      result = table.group_by("id").aggregate([("value", "mean_udf")])
      expected = pa.table(
          [pa.array([], pa.int32()), pa.array([], pa.float64())],
          names=["id", "value_mean_udf"],
      )
  
      assert result == expected
  
imports: import pytest
  import numpy
  import pyarrow
  from pyarrow import compute
label_desc: Use image node_id 53 for calling a global function with example usage: test_hash_agg_empty(unary_agg_func_fixture) without return types