Assign weight 1.0 to only the inputs for the given task.

def weights_multi_problem_input(labels, taskid=-1):
  """Assign weight 1.0 to only the inputs for the given task."""
  taskid = check_nonnegative(taskid)
  weights_all_tokens = weights_multi_problem_all(labels, taskid)
  weights_target = weights_multi_problem(labels, taskid)
  return weights_all_tokens - weights_target