 ///   `@dynamicCallable` attribute because the call syntax is unintuitive:
 ///   `x.throwing(arg1, arg2, ...)`. The methods will still be named
 ///   `dynamicallyCall` until further discussion/design.
-@frozen
 public struct ThrowingPythonObject {
   private var base: PythonObject
 

/// a Python C API `PyObject`.
@dynamicCallable
@dynamicMemberLookup
@frozen
public struct PythonObject {
  /// The underlying `PyReference`.
  fileprivate var reference: PyReference

/// Member access operations return an `Optional` result. When member access
/// fails, `nil` is returned.
@dynamicMemberLookup
public struct CheckingPythonObject {
  /// The underlying `PythonObject`.
  private var base: PythonObject
