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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 tf2():
 """Provide the root module of a TF-2.0 API for use within TensorBoard. Returns: The root module of a TF-2.0 API, if available. Raises: ImportError: if a TF-2.0 API is not available. """

  # Import the `tf` compat API from this file and check if it's already TF 2.0.
  if tf.__version__.startswith('2.'):
    return tf
  elif hasattr(tf, 'compat') and hasattr(tf.compat, 'v2'):
    # As a fallback, try `tensorflow.compat.v2` if it's defined.
    return tf.compat.v2
  raise ImportError('cannot import tensorflow 2.0 API')