private ReactionRole role(IAtom atom) {
        ReactionRole role = atom.getProperty(CDKConstants.REACTION_ROLE);
        if (role != null)
            return role;
        return ReactionRole.None;
    }
private ReactionRole role ( IAtom atom ) { ReactionRole role = atom . getProperty ( CDKConstants . REACTION_ROLE ) ; if ( role != null ) return role ; return ReactionRole . None ; }
Safely access the reaction role of an atom, returns {@link ReactionRole#None} if null.

@param atom atom
@return mapidx, None if undefined