下面是一个使用Python的示例代码，演示如何标注路线并扩展现有方法内部：

from typing import List

def annotate_route(route: List[str]) -> List[str]:
    annotated_route = []
    
    for i, step in enumerate(route):
        annotated_step = f"Step {i+1}: {step}"  # 添加步骤序号
        annotated_route.append(annotated_step)
    
    return annotated_route

def extend_method(route: List[str]) -> List[str]:
    extended_route = []
    
    for step in route:
        extended_step = f"Extended step: {step}"  # 扩展每个步骤
        extended_route.append(extended_step)
    
    return extended_route

# 示例用法
route = ["Turn left", "Go straight", "Turn right"]
annotated_route = annotate_route(route)
extended_route = extend_method(annotated_route)

print("Annotated Route:")
for step in annotated_route:
    print(step)

print("Extended Route:")
for step in extended_route:
    print(step)

输出结果：

Annotated Route:
Step 1: Turn left
Step 2: Go straight
Step 3: Turn right
Extended Route:
Extended step: Step 1: Turn left
Extended step: Step 2: Go straight
Extended step: Step 3: Turn right

在上述示例中，annotate_route函数将给每个步骤添加了步骤序号，并返回了一个新的带有标注的路线。然后，extend_method函数扩展了每个步骤，并返回了一个新的扩展后的路线。最后，我们打印出了标注和扩展后的路线。