@Override
        public Void timestampShape(TimestampShape shape) {
            if (shape.hasTrait(TimestampFormatTrait.ID)) {
                switch (shape.expectTrait(TimestampFormatTrait.class).getFormat()) {
                    case EPOCH_SECONDS:
                        writer.write("$T.from($L.getEpochSecond())", Node.class, varName);
                        return null;
                    case HTTP_DATE:
                        writer.write("$T.from($T.RFC_1123_DATE_TIME.format($L))",
                                Node.class,
                                DateTimeFormatter.class,
                                varName);
                        return null;
                    default:
                        // Fall through on default
                        break;
                }
            }
            toStringMapper();
            return null;
        }
Determines how to map a shape to a node.
smithy-trait-codegen/src/main/java/software/amazon/smithy/traitcodegen/generators/ToNodeGenerator.java