code: def test_no_conversion_equal(dataframe):
      df = dataframe.convert_units(
          "a",
          existing_units="cm",
          to_units="cm",
          dest_column_name="a_cm",
      )
      assert all(df["a"] == df["a_cm"])
  
file_path: pyjanitor/tests/engineering/test_convert_units.py
imports: import pytest
  from unyt.exceptions import UnitConversionError
  from janitor.engineering import convert_units
label_desc: Use image node_id 4 for calling a global function with example usage: test_no_conversion_equal(dataframe) without return types