code: @Override
  	public Atom getOther(Atom exclude) {
  		if (exclude != atomA && exclude != atomB) {
  			throw new IllegalArgumentException(
  					"Atom to exclude is not in bond.");
  		}
  
  		if (exclude == atomA) {
  			return atomB;
  		} else {
  			return atomA;
  		}
  	}
docs: A utility method to get the other atom in a bond, given one of its atoms.
  If the atom passed is one of the atoms in this bond, then this method is
  essentially equivalent to saying
  <code>atom == bond.getAtomA() ? bond.getAtomB() : bond.getAtomA()</code>.
  <p>
  <i>Note:</i> Comparison of atoms in this method is done with
  <code>==</code>, not <code>equals</code>.
  
  @param exclude the atom of the bond to not return
  @throws IllegalArgumentException if the passed atom is not in this bond
  @return the atom in this bond that was not passed as an argument