Cached Property Manual

Write a decorator `cached_property` that can be applied to a method of a class. When accessed as an attribute on an instance, the method is called once and its return value is stored on the instance for all subsequent accesses. The decorator must work correctly per instance (not share cache across instances). It must not interfere with attribute deletion or reassignment: if the attribute is deleted from the instance, the next access should recompute the property. It should raise the same exceptions as a normal property if the method raises. Define the decorator with the exact signature: ```python def cached_property(func): ... ``` The decorator should return a descriptor object (or use `property` with a caching getter). The cached value must be stored under attribute name `'_cached_' + func.__name__` on the instance. When the attribute is deleted, the cache is removed and recomputation occurs. The decorated method can be called directly via the class, e.g., `MyClass.method(instance)`, and should behave as a normal function in that case. Implement only the decorator and any helper classes/functions needed. Your code will be tested by applying the decorator to sample methods and checking behavior.

>>> class Example:
...     @cached_property
...     def value(self):
...         print('computing')
...         return 42
>>> e = Example()
>>> e.value
computing
42
>>> e.value
42
>>> del e.value
>>> e.value
computing
42
>>> f = Example()
>>> f.value  # computes again for a new instance
computing
42