@classmethod
def clearOwner(cls, f0):
    """Return a copy of f0 with no owner specified, or None if f0 is None."""
    if (f0 is None or f0.dataset is None and f0.sizeGeq is None and f0.
        mtime is None and f0.notPaths == [] and f0.regex is None):
        return None
    else:
        return cls(None, f0.dataset, f0.sizeGeq, f0.mtime, f0.notPaths, f0.
            regex)
