code: def test_mmcif_pdb_conversion():
      """Tests conversion from mmCIF df to PDB df"""
      # Multichain test
      pdb = PandasPdb().fetch_pdb("4hhb")
      mmcif = PandasMmcif().fetch_mmcif("4hhb")
      mmcif_pdb = mmcif.convert_to_pandas_pdb()
  
      assert_frame_equal(
          pdb.df["ATOM"].drop(columns=["line_idx"]),
          mmcif_pdb.df["ATOM"].drop(columns=["line_idx"]),
      )
      assert_frame_equal(
          pdb.df["HETATM"].drop(columns=["line_idx"]),
          mmcif_pdb.df["HETATM"]
          .drop(columns=["line_idx"])
          .reset_index(drop=True),
      )
  
      # single chain test
      pdb = PandasPdb().fetch_pdb("3eiy")
      mmcif = PandasMmcif().fetch_mmcif("3eiy")
      mmcif_pdb = mmcif.convert_to_pandas_pdb()
  
      assert_frame_equal(
          pdb.df["ATOM"].drop(columns=["line_idx"]),
          mmcif_pdb.df["ATOM"].drop(columns=["line_idx"]),
      )
      assert_frame_equal(
          pdb.df["HETATM"].drop(columns=["line_idx"]),
          mmcif_pdb.df["HETATM"]
          .drop(columns=["line_idx"])
          .reset_index(drop=True),
      )
  
imports: import os
  from urllib.error import HTTPError
  from urllib.request import urlopen
  from pathlib import Path
  import numpy
  import pandas
  from biopandas.mmcif import PandasMmcif
  from biopandas.pdb import PandasPdb
  from biopandas.testutils import assert_raises
  from nose.tools import raises
  from pandas.testing import assert_frame_equal
label_desc: Use image node_id 13 for calling a global function with example usage: test_mmcif_pdb_conversion() without return types