It looks like you need to go to Unity's website to get the package you're looking for. I imagine you're looking for the unity framework for iOS? Or are you trying to write code in Unity? If so, then you definitely need to go to the Unity website, and then download their IDE and that will include all of their libraries. Once you've made an app in Unity you can then export it, and then you can upload it to iTunesConnect (using your Apple Developer account)
The Code is listed in the Siri Forum Kit on the developers...
INSendMessageIncidentResponceKit; : XCSourceEditorCommandInvocation\
The Siri Incident Responce Kit also cleary states that, it wont be availabe, if the Incident Responce is In Progress or In Failure or Active.
The Code for that is:
INSendMessageIncidentResponceKit; : XCSourceEditorCommandSUCcceSSs
Text code Signature Invalid for Siri
The code for that is: