message: Fix KeyError when validation_data was given as a dict
  This fix tries to address the issue raised in 30122 where
  a KeyError was thrown when validation_data was given as a dict
  during the mode.fit. This fix fixes the issue.
  Thisfix fixes 30122.
diff: @@ -207,7 +207,8 @@ def model_iteration(model,
  val_samples_or_steps = validation_steps
  else:
  # Get num samples for printing.
  - val_samples_or_steps = val_inputs and val_inputs[0].shape[0] or None
  + vals = val_inputs.values() if isinstance(val_inputs, dict) else val_inputs
  + val_samples_or_steps = vals and vals[0].shape[0] or None
  if mode == ModeKeys.TRAIN and verbose:
  _print_train_info(num_samples_or_steps, val_samples_or_steps, is_dataset)
  