code: def test_nth():
      df = DataFrame([[1, np.nan], [1, 4], [5, 6]], columns=["A", "B"])
      gb = df.groupby("A")
  
      tm.assert_frame_equal(gb.nth(0), df.iloc[[0, 2]])
      tm.assert_frame_equal(gb.nth(1), df.iloc[[1]])
      tm.assert_frame_equal(gb.nth(2), df.loc[[]])
      tm.assert_frame_equal(gb.nth(-1), df.iloc[[1, 2]])
      tm.assert_frame_equal(gb.nth(-2), df.iloc[[0]])
      tm.assert_frame_equal(gb.nth(-3), df.loc[[]])
      tm.assert_series_equal(gb.B.nth(0), df.B.iloc[[0, 2]])
      tm.assert_series_equal(gb.B.nth(1), df.B.iloc[[1]])
      tm.assert_frame_equal(gb[["B"]].nth(0), df[["B"]].iloc[[0, 2]])
  
      tm.assert_frame_equal(gb.nth(0, dropna="any"), df.iloc[[1, 2]])
      tm.assert_frame_equal(gb.nth(-1, dropna="any"), df.iloc[[1, 2]])
  
      tm.assert_frame_equal(gb.nth(7, dropna="any"), df.iloc[:0])
      tm.assert_frame_equal(gb.nth(2, dropna="any"), df.iloc[:0])
  
imports: import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Index, MultiIndex, Series, Timestamp, isna
  import pandas._testing
label_desc: Use image node_id 10 for calling a global function with example usage: test_nth() without return types