/*
 This source file is part of the Swift.org open source project

 Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
 Licensed under Apache License v2.0 with Runtime Library Exception

 See http://swift.org/LICENSE.txt for license information
 See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 */

extension Collection {
    /// Returns the only element of the collection or nil.
    public var only: Element? {
        return count == 1 ? self[startIndex] : nil
    }

    /// Prints the element of array to standard output stream.
    ///
    /// This method should be used for debugging only.
    public func dump() {
        for element in self {
            print(element)
        }
    }
}

/*
 This source file is part of the Swift.org open source project

 Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
 Licensed under Apache License v2.0 with Runtime Library Exception

 See http://swift.org/LICENSE.txt for license information
 See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 */

extension Collection {
    /// Returns the only element of the collection or nil.
    public var only: Element? {
        return count == 1 ? self[startIndex] : nil
    }
}

--- 
+++ 
@@ -13,4 +13,13 @@
     public var only: Element? {
         return count == 1 ? self[startIndex] : nil
     }
+
+    /// Prints the element of array to standard output stream.
+    ///
+    /// This method should be used for debugging only.
+    public func dump() {
+        for element in self {
+            print(element)
+        }
+    }
 }
[Basic] Add dump method to Collections for debugging
