code: def test__ros_group_rank():
      df = pandas.DataFrame(
          {
              "dl_idx": [1] * 12,
              "params": list("AABCCCDE") + list("DCBA"),
              "values": list(range(12)),
          }
      )
  
      result = ros._ros_group_rank(df, "dl_idx", "params")
      expected = pandas.Series(
          [1, 2, 1, 1, 2, 3, 1, 1, 2, 4, 2, 3], name="rank"
      )
      assert_series_equal(result.astype(int), expected.astype(int))
  
imports: from statsmodels.compat.pandas import assert_series_equal, assert_frame_equal
  from io import StringIO
  from textwrap import dedent
  import numpy
  import numpy.testing
  import numpy
  from numpy.testing import assert_equal
  import pandas
  import pytest
  from statsmodels.imputation import ros
label_desc: Use image node_id 5 for calling a global function with example usage: test__ros_group_rank() without return types