Roughly speaking, the general idea of a decorator is to create a function that returns a function (often called a higher-order function). The internal function defined in the body of the decorator is going to be the one actually being called.
Now, if we wish to pass parameters to it, we then need another level of indirection. The first one will take the parameters, and inside that function, we will define a new function, which will be the decorator, which in turn will define yet another new function, namely the one to be returned as a result of the decoration process. This means that we will have at least three levels of nested functions.
Don't worry if this didn't seem clear so far. After reviewing the examples ...
