message: Logging function modification again
diff: @@ -926,7 +926,8 @@ class GradientTape(object):
  if self._tape is None:
  raise RuntimeError("GradientTape.gradient can only be called once on "
  "non-persistent tapes.")
  - if not is_floating(self._tape):
  + for v in target:
  + if not is_floating(v):
  raise ValueError("GradientTape.gradient can only be called when "
  "data type is float.")
  