decorator

Install the library using pip: `pip install decorator`

Ensure you are using `decorator.decorate` correctly to create the decorator, or that your custom decorator function returns a callable. For example, to create a simple decorator preserving signature: `from decorator import decorator
@decorator
def my_decorator(func, *args, **kwargs):
    print('Before function call')
    result = func(*args, **kwargs)
    print('After function call')
    return result

@my_decorator
def my_function():
    return 'Hello'`

Ensure that the expression after `@` is a valid callable (e.g., a function name, `module.function_name`, or a function call that returns a callable). Complex expressions like `@(lambda f: f)` or chained calls like `@f()()` are not allowed directly. You might need to assign the result of a complex expression to a variable first, then use that variable as the decorator. The `decorator` library's `decorate` function is designed to handle more complex programmatic decorator creation, but the `@` syntax itself has strict rules. Example of incorrect vs. correct usage:
```python
# Incorrect
# @(lambda f: f)
# def my_func(): pass

# Correct (assign lambda to a name first)
identity_decorator = lambda f: f
@identity_decorator
def my_func():
    pass

# If using 'decorator' library to build a decorator factory:
from decorator import decorator

def my_decorator_factory(arg):
    @decorator
    def my_actual_decorator(func, *args, **kwargs):
        print(f'Decorator arg: {arg}')
        return func(*args, **kwargs)
    return my_actual_decorator

@my_decorator_factory('test')
def another_func():
    return 'World'
```