code: public static SSBondImpl toSsBond(Bond bond) {
  
  		if (!bond.getAtomA().getGroup().getPDBName().equals("CYS") ||
  			!bond.getAtomB().getGroup().getPDBName().equals("CYS")    ) {
  
  			throw new IllegalArgumentException("Trying to create a SSBond from a Bond between 2 groups that are not CYS");
  		}
  
  		SSBondImpl ssbond = new SSBondImpl();
  		ssbond.setChainID1(bond.getAtomA().getGroup().getChainId());
  		ssbond.setChainID2(bond.getAtomB().getGroup().getChainId());
  		ssbond.setResnum1(String.valueOf(bond.getAtomA().getGroup().getResidueNumber().getSeqNum()));
  		ssbond.setResnum2(String.valueOf(bond.getAtomB().getGroup().getResidueNumber().getSeqNum()));
  
  		Character iCode1 = bond.getAtomA().getGroup().getResidueNumber().getInsCode();
  		if (iCode1 == null) iCode1 = ' ';
  		Character iCode2 = bond.getAtomB().getGroup().getResidueNumber().getInsCode();
  		if (iCode2 == null) iCode2 = ' ';
  
  		ssbond.setInsCode1(String.valueOf(iCode1));
  		ssbond.setInsCode2(String.valueOf(iCode2));
  
  		return ssbond;
  	}
docs: Converts the given {@link Bond} object into a {@link SSBondImpl}.
  
  @return
  @throws IllegalArgumentException if this Bond is not between two CYS residues