Imperative mode prototype

Signed-off-by: Michal Zientkiewicz <michalz@nvidia.com>

Author: mzient

dali/python/nvidia/dali/experimental/dali2/__init__.py

@@ -17,6 +17,13 @@
 """
 
 from ._eval_mode import EvalMode  # noqa: F401
-from ._eval_context import EvalContext  # noqa: F401
 from ._type import *  # noqa: F401, F403
+from ._tensor import Tensor, tensor, as_tensor  # noqa: F401
+from ._batch import Batch, batch, as_batch  # noqa: F401
 from ._device import Device  # noqa: F401
+
+from . import _fn
+from . import ops
+
+ops._initialize()
+_fn._initialize()