      backend: ["amd", "cpu", "nvidia", "apple_silicon"]
          The backend to set faceswap to
      """
      global _FS_BACKEND  # pylint:disable=global-statement
      _FS_BACKEND = backend.lower()
  
  
  def get_tf_version():
      """ Obtain the major.minor version of currently installed Tensorflow.
  
 
</s> remove def get_tf_version():
 </s> add def get_tf_version() -> float: </s> remove def set_backend(backend):
 </s> add def set_backend(backend: str) -> None: </s> remove def get_backend():
 </s> add def get_backend() -> ValidBackends: </s> remove _FS_BACKEND = _Backend().backend
 </s> add _FS_BACKEND: ValidBackends = _Backend().backend
    backend = cast(ValidBackends, backend.lower())
    _FS_BACKEND = backend
      backend: ["amd", "cpu", "nvidia", "apple_silicon"]
          The backend to set faceswap to
      """
      global _FS_BACKEND  # pylint:disable=global-statement
    backend = cast(ValidBackends, backend.lower())
    _FS_BACKEND = backend
  
  
  def get_tf_version():
      """ Obtain the major.minor version of currently installed Tensorflow.
  
keep keep keep keep replace keep keep keep keep keep
 lib.Utils - add DPI detector 
lib/utils.py