I am having an issue with some error in the following dataweave

In the following dataweave

%dw 2.0

output application/json

var location = attributes.headers.location default '' splitBy'/'

---

{

   id: location[sizeOf(location) -1],

   firstName: vars.userCreationJson.firstName,

   lastName: vars.userCreationJson.lastName,

   email: vars.userCreationJson.email,

   password: vars.password,

   requiredActions: ['UPDATE PASSWORD']

}

var location = attributes.headers.location default '' splitBy'/' has an error of Unable to resolve reference of splitBy.

 id: location[sizeOf(location) -1] has an error of Unable to resolve reference of sizeOf.

The output is a defined example, the input is not.

I am not sure if I am doing the dataweave wrong or it is just a "phantom" error since the dataweave itself returns what I am looking for. ie the last element in the url

Speaking of which is there a better way of getting the id from the end of a location url?

ie http://thisurl.com/something/something/25356653 <-id