code: private IAtomContainer getMoleculeFromID(IAtomContainerSet molSet, String id) {
          for (IAtomContainer mol : molSet.atomContainers()) {
              if (mol.getID().equals(id)) return mol;
          }
          return null;
      }
docs: Get the IAtomContainer contained in a IAtomContainerSet object with a ID.
  
  @param molSet   The IAtomContainerSet
  @param id       The ID the look
  @return         The IAtomContainer with the ID