message: Do not ensure_initialized() in Function.__call__
  It turns out the call is not necessary according to tests. Removing it
  makes the function more generic and slightly faster.
diff: @@ -559,7 +559,6 @@ class Function(object):
  def __call__(self, *args, **kwds):
  """Calls the graph function and warn too frequent tracings."""
  - context.ensure_initialized()
  if RUN_FUNCTIONS_EAGERLY:
  return self._python_function(*args, **kwds)
  