message: Initialize the context before accessing its handle in Context.*function
diff: @@ -719,6 +719,7 @@ class Context(object):
  Args:
  fn: A wrapped TF_Function (returned from TF_GraphToFunction_wrapper).
  """
  + self.ensure_initialized()
  pywrap_tensorflow.TFE_ContextAddFunction(self._handle, fn)
  def add_function_def(self, fdef):
  @@ -730,12 +731,14 @@ class Context(object):
  Args:
  fdef: A FunctionDef protocol buffer message.
  """
  + self.ensure_initialized()
  fdef_string = fdef.SerializeToString()
  pywrap_tensorflow.TFE_ContextAddFunctionDef(
  self._handle, fdef_string, len(fdef_string))
  def has_function(self, name):
  """Check if a function `name` is registered."""
  + self.ensure_initialized()
  return bool(pywrap_tensorflow.TFE_ContextHasFunction(self._handle, name))
  def add_post_execution_callback(self, callback):
  