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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def tf():
 """Provide the root module of a TF-like API for use within TensorBoard. By default this is equivalent to `import tensorflow as tf`, but it can be used in combination with //tensorboard/compat:tensorflow (to fall back to a stub TF API implementation if the real one is not available) or with //tensorboard/compat:no_tensorflow (to force unconditional use of the stub). Returns: The root module of a TF-like API, if available. Raises: ImportError: if a TF-like API is not available. """

  try:
    from tensorboard.compat import notf  # pylint: disable=g-import-not-at-top
  except ImportError:
    try:
      import tensorflow  # pylint: disable=g-import-not-at-top
      return tensorflow
    except ImportError:
      pass
  from tensorboard.compat import tensorflow_stub  # pylint: disable=g-import-not-at-top
  return tensorflow_stub