<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _varargs_labels_as_list(label_list):
 """Return a list of labels for a list of labels or singleton list of list of labels."""

    if len(label_list) == 0:
        return []
    elif not _is_non_string_iterable(label_list[0]):
        # Assume everything is a label.  If not, it'll be caught later.
        return label_list
    elif len(label_list) == 1:
        return label_list[0]
    else:
        raise ValueError("Labels {} contain more than list.".format(label_list),
                         "Pass just one list of labels.")