item = dicMyList[key]
        if item != nil {
            // add it to existing list
            dicMyList[key]!.list.append(filename)
//            item?.list.append(filename)
        }

// example setup
var dicMyList = [1: ["foo.sig", "bar.cc"]] // [Int: [String]] dict
var key = 1
var fileName = "baz.h"

// "append" (copy-in/copy-out) 'fileName' to inner array associated
// with 'key'; constructing a new key-value pair in case none exist
dicMyList[key] = (dicMyList[key] ?? []) + [fileName]
print(dicMyList) // [1: ["foo.sig", "bar.cc", "baz.h"]]

// same method used for non-existant key
key = 2
fileName = "bax.swift"
dicMyList[key] = (dicMyList[key] ?? []) + [fileName]
print(dicMyList) // [2: ["bax.swift"], 1: ["foo.sig", "bar.cc", "baz.h"]]

if var list = dicMyList[key] {
    list.append(filename)
    dicMyList[key] = list
} else {
    dicMyList[key] = [filename]
}

extension Optional where Wrapped == Array<String> {

    mutating func append(_ element: String) {
        if self == nil {
            self = [element]
        }
        else {
            self!.append(element)
        }
    }
}

var dictionary = [String: [String]]()

dictionary["Hola"].append("Chau")