code: @Override
      public DescriptorValue calculate(IAtomContainer container) {
          double apol = 0;
          int atomicNumber;
          try {
              IsotopeFactory ifac = Isotopes.getInstance();
              IElement element;
              String symbol;
              for (IAtom atom : container.atoms()) {
                  symbol = atom.getSymbol();
                  element = ifac.getElement(symbol);
                  atomicNumber = element.getAtomicNumber();
                  apol += polarizabilities[atomicNumber];
                  if (atom.getImplicitHydrogenCount() != CDKConstants.UNSET) {
                      apol += polarizabilities[1] * atom.getImplicitHydrogenCount();
                  }
              }
              return new DescriptorValue(getSpecification(), getParameterNames(), getParameters(),
                      new DoubleResult(apol), getDescriptorNames());
          } catch (Exception ex1) {
              logger.debug(ex1);
              return new DescriptorValue(getSpecification(), getParameterNames(), getParameters(), new DoubleResult(
                      Double.NaN), getDescriptorNames(), new CDKException("Problems with IsotopeFactory due to "
                      + ex1.toString(), ex1));
          }
      }
docs: Calculate the sum of atomic polarizabilities in an {@link IAtomContainer}.
  
  @param  container  The {@link IAtomContainer} for which the descriptor is to be calculated
  @return The sum of atomic polarizabilities
  {@link org.openscience.cdk.config.XMLIsotopeFactory}