Remove _backend folder (#4041)

Author: samanklesaria

src/torchaudio/__init__.py

@@ -2,24 +2,12 @@
 from typing import Union, BinaryIO, Optional, Tuple
 import os
 import torch
+import sys
 
 # Initialize extension and backend first
 from . import _extension  # noqa  # usort: skip
-from ._backend import (  # noqa  # usort: skip
-    AudioMetaData as _AudioMetaData,
-    get_audio_backend as _get_audio_backend,
-    info as _info,
-    list_audio_backends as _list_audio_backends,
-    set_audio_backend as _set_audio_backend,
-)
 from ._torchcodec import load_with_torchcodec, save_with_torchcodec
 
-AudioMetaData = dropping_class_io_support(_AudioMetaData)
-get_audio_backend = dropping_io_support(_get_audio_backend)
-info = dropping_io_support(_info)
-list_audio_backends = dropping_io_support(_list_audio_backends)
-set_audio_backend = dropping_io_support(_set_audio_backend)
-
 from . import (  # noqa: F401
     compliance,
     datasets,
@@ -33,8 +21,6 @@
     utils,
 )
 
-# For BC
-from . import backend  # noqa # usort: skip
 
 try:
     from .version import __version__, git_version  # noqa: F401
@@ -209,11 +195,9 @@ def save(
         compression=compression)
 
 __all__ = [
-    "AudioMetaData",
     "load",
     "load_with_torchcodec",
     "save_with_torchcodec",
-    "info",
     "save",
     "io",
     "compliance",
@@ -225,7 +209,4 @@ def save(
     "utils",
     "sox_effects",
     "transforms",
-    "list_audio_backends",
-    "get_audio_backend",
-    "set_audio_backend",
 ]