code: def test_ligand_default():
      r = PandasPdb.rmsd(pl1.df["HETATM"], pl2.df["HETATM"], s=None)
      assert r == 2.6444, r
  
file_path: biopandas/biopandas/pdb/tests/test_rmsd.py
imports: from biopandas.pdb import PandasPdb
  import os
  from nose.tools import raises
label_desc: Use image node_id 8 for calling a global function with example usage: test_ligand_default() without return types