code: def test_merge_molecules(self):
      current_dir = os.path.dirname(os.path.realpath(__file__))
      ligand_file = os.path.join(
          current_dir, "../../dock/tests/1jld_ligand.sdf"
      )
      xyz, mol = rdkit_utils.load_molecule(
          ligand_file, calc_charges=False, add_hydrogens=False
      )
      num_mol_atoms = mol.GetNumAtoms()
      # self.ligand_file is for 3ws9_ligand.sdf
      oth_xyz, oth_mol = rdkit_utils.load_molecule(
          self.ligand_file, calc_charges=False, add_hydrogens=False
      )
      num_oth_mol_atoms = oth_mol.GetNumAtoms()
      merged = rdkit_utils.merge_molecules([mol, oth_mol])
      merged_num_atoms = merged.GetNumAtoms()
      assert merged_num_atoms == num_mol_atoms + num_oth_mol_atoms
  
imports: import tempfile
  import unittest
  import os
  import numpy
  from deepchem.utils import rdkit_utils
label_desc: Use image node_id 11 for calling the TestRdkitUtil obj's underlying member method code with example usage: obj.test_merge_molecules() without return types