code: def test_categorical_head_tail(method, observed, sort, as_index):
      # GH#36327
      values = np.random.default_rng(2).choice([1, 2, None], 30)
      df = pd.DataFrame(
          {
              "x": pd.Categorical(values, categories=[1, 2, 3]),
              "y": range(len(values)),
          }
      )
      gb = df.groupby(
          "x",
          dropna=False,
          observed=observed,
          sort=sort,
          as_index=as_index,
      )
      result = getattr(gb, method)()
  
      if method == "tail":
          values = values[::-1]
      # Take the top 5 values from each group
      mask = (
          ((values == 1) & ((values == 1).cumsum() <= 5))
          | ((values == 2) & ((values == 2).cumsum() <= 5))
          # flake8 doesn't like the vectorized check for None, thinks we should use `is`
          | (
              (values == None) & ((values == None).cumsum() <= 5)
          )  # noqa: E711
      )
      if method == "tail":
          mask = mask[::-1]
      expected = df[mask]
  
      tm.assert_frame_equal(result, expected)
  
imports: import numpy
  import pytest
  from pandas.compat.pyarrow import pa_version_under10p1
  from pandas.core.dtypes.missing import na_value_for_dtype
  import pandas
  import pandas._testing
  from pandas.tests.groupby import get_groupby_method_args
label_desc: Use image node_id 18 for calling a global function with example usage: test_categorical_head_tail(method, observed, sort, as_index) without return types