code: def test_ligand():
      r = PandasPdb.rmsd(
          pl1.df["HETATM"], pl2.df["HETATM"], s="hydrogen", invert=True
      )
      assert r == 1.9959, 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 7 for calling a global function with example usage: test_ligand() without return types