Removes the specified number of elements from the beginning of the collection.
- iOS 7.0+
- macOS 10.9+
- tvOS 9.0+
- watchOS 2.0+
- Xcode 10.0+
The number of elements to remove from the collection.
kmust be greater than or equal to zero and must not exceed the number of elements in the collection.
Calling this method may invalidate any existing indices for use with this collection.
Complexity: O(n), where n is the length of the collection.