Editor placeholder in source fileが出てしまう。

Question

import UIKit
import Firebase
import QuartzCore
//import FirebaseAuth
//import FirebaseDatabase

class AddViewController: UIViewController {
    @IBOutlet var contentTextView:  UITextView! 
    
    var me: AppUser!

    override func viewDidLoad() {
        super.viewDidLoad()
        
        contentTextView.layer.borderColor = UIColor.red.cgColor


        contentTextView.layer.borderWidth = 1.0

        contentTextView.layer.cornerRadius = 10.0
        contentTextView.layer.masksToBounds = true
    }
    
    
    @IBAction func postContent() {
        let content = contentTextView.text!
        let user = AppUser.init(data: <#T##[String : Any]#>)
        let saveDocument = Firestore.firestore().collection("posts").document()
        _ = Auth.auth().currentUser!.uid
        saveDocument.setData([
            "content": content,
            "postID": saveDocument.documentID,
            "senderID": user.uid,
            "createdAt": FieldValue.serverTimestamp(),
            "updatedAt": FieldValue.serverTimestamp()
        ]) { error in
            if error == nil {
                self.dismiss(animated: true, completion: nil)
            }
        }
    }
    
    func setupTextView() {
        let toolBar = UIToolbar() 
        let flexibleSpaceBarButton = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil) 
        let doneButton = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(dismissKeyboard)) 
        toolBar.items = [flexibleSpaceBarButton, doneButton] 
        toolBar.sizeToFit()
        contentTextView.inputAccessoryView = toolBar 
    }

    @objc func dismissKeyboard() {
        contentTextView.resignFirstResponder()
    }
    
}

Answer 1

値を入れないといけないところに入っていないよというエラーです。
下記の<#T##[String : Any]#>だと思います。

let user = AppUser.init(data: <#T##[String : Any]#>)

書いてあるように
[String: Any]型のものを書いてくださいってことです。