message: Clarify tf.function documentation for experimental_compile
  Fix the tenses used.
diff: @@ -382,20 +382,20 @@ class Function(object):
  conversion options when autograph is set to True.
  experimental_relax_shapes: When true, argument shapes may be relaxed to
  avoid unnecessary retracing.
  - experimental_compile: If false, execute the function in a regular way. The
  - function is optimized by some graph rewrite passes (some ops might be
  - clustered into a single op) and interpreted by the standard TensorFlow
  - executor, which dispatches op kernels one by one as they become
  - executable. Set it to false when directly running a multi-device
  - function on TPUs (e.g. two TPU cores, one TPU core and its
  - host CPU). If True, the function is compiled directly by XLA. XLA would
  - fuse all the ops and emit more efficient code to run for some devices
  - (e.g. TPU, XLA_GPU) and some use cases (e.g. dense tensor computation).
  - It requires that the whole function is compilable by XLA. If None
  - (default), compile the function with XLA when running on TPU and go
  - through the regular function execution path when running on other
  - devices.
  -
  + experimental_compile: If `True`, compiles the function using XLA
  + (see https://tensorflow.org/xla). XLA performs compiler optimizations,
  + such as fusion, and attempts to emit more efficient code. This may
  + drastically improve the performance. If set to `True`,
  + the whole function needs to be compilable by XLA, or an
  + `errors.InvalidArgumentError` is thrown.
  + If `None` (default), compiles the function with XLA when running on TPU
  + and goes through the regular function execution path when running on
  + other devices.
  + If `False`, executes the function in a regular way (graph rewrite
  + passes are applied, kernels are dispatched one-by-one by the TensorFlow
  + executor). Set this value to `False` when directly running a
  + multi-device function on TPUs (e.g. two TPU cores, one TPU core and its
  + host CPU).
  Raises:
  ValueError: if `input_signature` is not None and the `python_function`'s
  argspec has keyword arguments.
  