class.callback(fname) -> Function{String|Array}
If a string, it represents the function to be called.
If it is an array, it will call each function in order and pass the return value of the prior function to the
next function.
{Function}
the callback function
Returns a callback function. This does the same thing as and is described better in jQuery.Class.callback. The only difference is this callback works on a instance instead of a class.