docs: private List<String> parameters() throws RecognitionException {
          match( input,
                 DRL5Lexer.LEFT_PAREN,
                 null,
                 null,
                 DroolsEditorType.SYMBOL );
          if ( state.failed ) return null;
  
          List<String> parameters = new ArrayList<String>();
          if ( input.LA( 1 ) != DRL5Lexer.EOF && input.LA( 1 ) != DRL5Lexer.RIGHT_PAREN ) {
              String param = conditionalExpression();
              if ( state.failed ) return null;
              parameters.add( param );
  
              while ( input.LA( 1 ) == DRL5Lexer.COMMA ) {
                  match( input,
                         DRL5Lexer.COMMA,
                         null,
                         null,
                         DroolsEditorType.SYMBOL );
                  if ( state.failed ) return null;
  
                  param = conditionalExpression();
                  if ( state.failed ) return null;
                  parameters.add( param );
              }
          }
  
          match( input,
                 DRL5Lexer.RIGHT_PAREN,
                 null,
                 null,
                 DroolsEditorType.SYMBOL );
          if ( state.failed ) return null;
          return parameters;
      }