code: def test_negative_k(df):
      """Raises Value Error if k is less than 1 (negative or 0)."""
      with pytest.raises(
          ValueError,
          match="Numbers of rows per group.+",
      ):
          df.groupby_topk("result", "age", -2)
  
file_path: pyjanitor/tests/functions/test_groupby_topk.py
imports: import pandas
  import pytest
  from pandas.testing import assert_frame_equal
label_desc: Use image node_id 8 for calling a global function with example usage: test_negative_k(df) without return types