code: private void checkBond(IAtomContainer atomContainer, int index) throws CDKException {
          IBond bond = atomContainer.getBond(index);
  
          if (bond != null && bond.getFlag(CDKConstants.SINGLE_OR_DOUBLE)) {
              try {
                  oldBondOrder = bond.getOrder();
                  bond.setOrder(IBond.Order.SINGLE);
                  setMaxBondOrder(bond, atomContainer);
              } catch (CDKException e) {
                  bond.setOrder(oldBondOrder);
                  logger.debug(e);
              }
          }
      }
docs: This method tries to set the bond order on the current bond.
  
  @param atomContainer The molecule
  @param index The index of the current bond
  @throws CDKException when no suitable solution can be found