Typescript Decorator on method; get method in decorator

I am trying to make a decorator that can:

1. Take a parameter
2. Store the method it is above as a callable function
3. Map the callable function with the parameter the decorator takes.

Here is what I tried:

class Foo {

    static cachedMethods: Map<string, (arg: string) => void> = new Map();

    static decorator = (decoratorArg: string) => (
        target: Object, 
        propertyKey: string,
        descriptor: TypedPropertyDescriptor<any>
        ): any => Foo.cachedMethods.set(decoratorArg, target as (arg: string) => void);

}

class Bar {
   @Foo.decorator("some data")
   method1(arg: string) {
      console.log(arg);
   }

   @Foo.decorator("some other data")
   method2(arg: string) {
       console.log(arg);
   }
}

let func: Function = Foo.cachedMethods.get("some data")!;
func("hello world");

However, it says that func is not a function. It is storing it as the Bar class. How can I store the method as a function?