code: private IAtom findAtomByPosition(IAtomContainer container, int position) {
          String pos = String.valueOf(position);
          for (IAtom atom : container.atoms()) {
              if (atom.getID().equals(pos)) return atom;
          }
          return null;
      }
docs: Helper method that locates an atom based on its InChI atom table
  position, which has been set as ID.
  @param container input container
  @param position InChI atom table position
  @return atom on the position