<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def legacy_signature(**kwargs_mapping):
 """ This decorator makes it possible to call a function using old argument names when they are passed as keyword arguments. @legacy_signature(old_arg1='arg1', old_arg2='arg2') def func(arg1, arg2=1):
 return arg1 + arg2 func(old_arg1=1) == 2 func(old_arg1=1, old_arg2=2) == 3 """


    def signature_decorator(f):
        @wraps(f)
        def wrapper(*args, **kwargs):
            redirected_kwargs = {
                kwargs_mapping[k] if k in kwargs_mapping else k: v
                for k, v in kwargs.items()
            }
            return f(*args, **redirected_kwargs)

        return wrapper

    return signature_decorator