code: private static boolean isPlanarSigmaBond(IBond bond) {
          return bond != null &&
                  IBond.Order.SINGLE.equals(bond.getOrder()) &&
                  IBond.Stereo.NONE.equals(bond.getStereo());
      }
docs: Helper method determines if a bond is defined (not null) and whether it
  is a sigma (single) bond with no stereo attribute (wedge/hatch).
  
  @param bond the bond to test
  @return the bond is a planar sigma bond