@Override
        public Void stringShape(StringShape shape) {
            if (shape.hasTrait(EnumTrait.class)) {
                LOGGER.finest(() -> "Generating string enum " + shape.getId());
                directedCodegen.generateEnumShape(new GenerateEnumDirective<>(context, serviceShape, shape));
            }
            return null;
        }
Finalizes the Runner and performs directed code generation.

@throws IllegalStateException if a required value has not been provided.
smithy-codegen-core/src/main/java/software/amazon/smithy/codegen/core/directed/CodegenDirector.java