code: private void prepareCoords(Iterable<IAtomContainer> mols) throws CDKException {
          for (IAtomContainer mol : mols) {
              if (!ensure2dLayout(mol) && mol.getBondCount() > 0) {
                  final double factor = GeometryUtil.getScaleFactor(mol, 1.5);
                  GeometryUtil.scaleMolecule(mol, factor);
              }
          }
      }
docs: Prepare a collection of molecules for rendering. If coordinates are not
  present they are generated, if coordinates exists they are scaled to
  be consistent (length=1.5).
  
  @param mols molecules
  @return coordinates
  @throws CDKException