message: Adjust export_keras
  Summary: Ref T57435
  Reviewers: alfiee, bartlomiejw, #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved
  Maniphest Tasks: T57435
diff: @@ -28,7 +28,6 @@ from tensorflow.python.ipu import application_compile_op
  from tensorflow.python.ipu import embedded_runtime
  from tensorflow.python.ipu import ipu_infeed_queue
  from tensorflow.python.ipu import ipu_outfeed_queue
  -from tensorflow.python.ipu import keras as ipu_keras
  from tensorflow.python.ipu import loops
  from tensorflow.python.ipu.ops import pipelining_ops
  from tensorflow.python.module import module
  @@ -382,8 +381,7 @@ def export_keras(model, export_dir):
  raise ValueError(
  "Directory is not empty. Please specify an empty directory.")
  - if not isinstance(
  - model, ipu_keras.extensions.keras_extension_base.KerasExtensionBase):
  + if not hasattr(model, 'export_for_ipu_serving'):
  raise ValueError(
  "Provided model was not created inside an IPU strategy, so it "
  "does not contain IPU-specific functions. Please wrap its "
  