'@param title: title or ``_(\'Unknown\')``
@param authors: List of strings or []
@param other: None or a metadata object'

def __init__(self, title, authors=(_('Unknown'),), other=None, template_cache=None, formatter=None):

    _data = copy.deepcopy(NULL_VALUES)
    _data.pop('language')
    object.__setattr__(self, '_data', _data)
    if (other is not None):
        self.smart_update(other)
    else:
        if title:
            self.title = title
        if authors:
            self.author = (list(authors) if authors else [])
            self.authors = (list(authors) if authors else [])
    from calibre.ebooks.metadata.book.formatter import SafeFormat
    self.formatter = (SafeFormat() if (formatter is None) else formatter)
    self.template_cache = template_cache
