code: def test_single_index(df):
      """Test output if df.columns is not a multiindex"""
      actual = df.change_index_dtype(dtype=float)
      expected = df.set_index(np.arange(0.0, len(df)))
      assert_frame_equal(expected, actual)
  
file_path: pyjanitor/tests/functions/test_change_index_dtype.py
imports: import numpy
  import pandas
  import pytest
  from pandas.testing import assert_frame_equal
label_desc: Use image node_id 11 for calling a global function with example usage: test_single_index(df) without return types