@classmethod
def escape_options(cls, options):
    """
        Escapes the items in the *options* list and prepends a '-' if
        necessairy.
        If *options* is None, the empty string will be returned.

        >>> TS3Escape.options_to_str(None)
        ''
        >>> TS3Escape.options_to_str([None, 'permsid', '-virtual'])
        '-permsid -virtual'

        :arg options: A list with the options.
        :type options: None or a list of strings.
        """
    if options is None:
        return str()
    tmp = list()
    for i, e in enumerate(options):
        if e is None:
            continue
        elif not e.startswith('-'):
            e = '-' + e
        tmp.append(e)
    tmp = ' '.join(tmp)
    return tmp
