Antlr3.Tool.Grammar.SetOption C# (CSharp) Method

        public virtual string SetOption( string key, object value, IToken optionsStartToken )
        {
            if ( LegalOption( key ) )
            {
                ErrorManager.GrammarError( ErrorManager.MSG_ILLEGAL_OPTION,
                                          this,
                                          optionsStartToken,
                                          key );
                return null;
            }
            if ( !OptionIsValid( key, value ) )
            {
                return null;
            }
            if ( key == "backtrack" && value.ToString() == "true" )
            {
                composite.RootGrammar.atLeastOneBacktrackOption = true;
            }
            if ( options == null )
            {
                options = new Dictionary<string, object>();
            }
            options[key] = value;
            return key;
        }