move session-related code to session.py submodule

Author: leogama

dill/__init__.py

@@ -24,13 +24,15 @@
 
 
 from ._dill import (
-    dump, dumps, load, loads, dump_module, load_module, load_module_asdict,
-    dump_session, load_session, is_module_pickle, Pickler, Unpickler, register,
-    copy, pickle, pickles, check, HIGHEST_PROTOCOL, DEFAULT_PROTOCOL,
-    PicklingError, UnpicklingError, HANDLE_FMODE, CONTENTS_FMODE, FILE_FMODE,
-    PickleError, PickleWarning, PicklingWarning, UnpicklingWarning,
+    Pickler, Unpickler,
+    check, copy, dump, dumps, load, loads, pickle, pickles, register,
+    DEFAULT_PROTOCOL, HIGHEST_PROTOCOL, CONTENTS_FMODE, FILE_FMODE, HANDLE_FMODE,
+    PickleError, PickleWarning, PicklingError, PicklingWarning, UnpicklingError,
+    UnpicklingWarning,
 )
-from . import source, temp, detect
+from .session import dump_module, is_module_pickle, load_module, load_module_asdict
+from .session import dump_session, load_session  # backward compatibility
+from . import detect, session, source, temp
 
 # get global settings
 from .settings import settings