message: Add support for partial targets use case in eager mode.
diff: @@ -59,6 +59,14 @@ def _eager_metrics_fn(model, outputs, targets, sample_weights=None, masks=None):
  # Invoke all(weighted and unweighted) metrics.
  metric_results = []
  if targets:
  + # Insert None values corresponding to the targets that need to be skipped
  + # on the model.
  + if len(model._targets) != len(targets):
  + new_targets = [
  + None if t is None else targets.pop(0) for t in model._targets
  + ]
  + targets = new_targets
  +
  metric_results = model._handle_metrics(
  outputs,
  targets=targets,
  