message: Minor spelling and grammar fixes in op_callbacks.py
diff: @@ -79,7 +79,7 @@ def add_op_callback(callback_fn):
  # "MatMul_2".
  # graph: The graph that the op belongs to (if any).
  # - In eager execution of an op or FuncGraph, this is `None`.
  - # - In graph construction, this is the op's containing graph
  + # - In graph construction, this is the op's enclosing graph
  # as a `tf.Graph` object.
  #
  # Return values:
  @@ -89,7 +89,7 @@ def add_op_callback(callback_fn):
  # `outputs` argument.
  # If the return value is `None`, downstream execution or graph
  # construction will be unaffected.
  - # Howevevr, if the return value is a `list` or `tuple` of `Tensor`s,
  + # However, if the return value is a `list` or `tuple` of `Tensor`s,
  # - In eager execution, these returned `Tensor`s should be
  # `EagerTensor`s. Their values will replace the original values of
  # `outputs` for downstream eager execution. (*Not implemented yet*).
  