<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _not_none(items):
 """Whether the item is a placeholder or contains a placeholder."""

    if not isinstance(items, (tuple, list)):
        items = (items,)
    return all(item is not _none for item in items)