Implement decision state machine (#8)

Author: timl3136

cadence/_internal/__init__.py

@@ -0,0 +1,10 @@
+"""Private implementation details for the Cadence Python client.
+
+Modules in this package are not part of the public API surface and may change
+without notice. Public callers should import from packages like `cadence.worker`,
+`cadence.workflow`, and `cadence.activity` instead.
+"""
+
+__all__: list[str] = []
+
+