 
   public var pythonObject: PythonObject {
     _ = Python // Ensure Python is initialized.
-    return PythonObject(sliceStart: lowerBound, stop: upperBound, step: nil)
+    return Python.slice(lowerBound, upperBound, Python.None)
   }
 }
 

/// Return true if the specified objects an instance of the low-level Python
/// type descriptor passed in as 'type'.
private func isType(_ object: PythonObject,
                    type: UnsafeMutableRawPointer) -> Bool {
  let typePyRef = PythonObject(borrowing: type)

  let result = Python.isinstance(object, typePyRef)


}

public extension PythonObject {
  // Tuples require explicit support because tuple types cannot conform to
  // protocols.
  init(tupleOf elements: PythonConvertible...) {
