code: def test_multiindex_one_key(nogil, parallel, nopython):
      pytest.importorskip("numba")
  
      def numba_func(values, index):
          return 1
  
      df = DataFrame([{"A": 1, "B": 2, "C": 3}]).set_index(["A", "B"])
      engine_kwargs = {
          "nopython": nopython,
          "nogil": nogil,
          "parallel": parallel,
      }
      result = df.groupby("A").agg(
          numba_func, engine="numba", engine_kwargs=engine_kwargs
      )
      expected = DataFrame(
          [1.0], index=Index([1], name="A"), columns=["C"]
      )
      tm.assert_frame_equal(result, expected)
  
imports: import numpy
  import pytest
  from pandas.errors import NumbaUtilError
  from pandas import DataFrame, Index, NamedAgg, Series, option_context
  import pandas._testing
label_desc: Use image node_id 13 for calling a global function with example usage: test_multiindex_one_key(nogil, parallel, nopython) and returns: int