code: @Override
      public DescriptorValue calculate(IAtom atom, IAtomContainer container) {
  
          IAtom focus = container.getAtom(focusPosition);
  
          // could be cached
          int bondsToAtom = new ShortestPaths(container, atom).distanceTo(focus);
  
          return new DescriptorValue(getSpecification(), getParameterNames(), getParameters(), new IntegerResult(
                  bondsToAtom), getDescriptorNames());
  
      }
docs: This method calculate the number of bonds on the shortest path between two atoms.
  
  @param  atom              The IAtom for which the DescriptorValue is requested
  @param  container         Parameter is the atom container.
  @return                   The number of bonds on the shortest path between two atoms