Preserve Function Metadata with functools.wraps

Summary

Learn to write decorators that preserve a function's metadata using functools.wraps.

Problem statement

When you write decorators in Python, a common pitfall is that the wrapper function hides metadata from the original function (like __name__ and __doc__). The functools.wraps helper copies metadata from the original function to the wrapper so tools like documentation generators, debugging, and introspection still work. Your task: write a decorator called preserve_metadata that: - Uses functools.wraps to ensure the wrapper preserves the original function's __name__, __doc__, and __wrapped__ (i.e., the original function must still be accessible via __wrapped__). - Calls the original function with the same arguments and returns its result. - Attaches an attribute named metadata to the wrapper function. This attribute should be a dict containing the key 'decorated' with the boolean value True. Provide a usable decorator so functions decorated with @preserve_metadata behave identically to the original function, except they have the additional metadata attribute.

Task

Implement a decorator that wraps another function while preserving its __name__, __doc__, and __wrapped__ metadata, and attaches a small metadata attribute to the wrapper.

Examples

Input format

A decorated function is defined in the provided code. Tests will call the decorated function or inspect its attributes.

Output format

Expressions should evaluate to values (strings, booleans, etc.). The test harness compares the stringified return value to the expected output.

Constraints

Use functools.wraps to preserve metadata. Attach the metadata attribute as a dict: {'decorated': True}. Do not modify the original function's behavior.

Samples