'Return the plural string (including nplurals) for this catalog language,
or None if no plural string is available.'

@property
def _plural_string(self):

    if ('' in self.translation._catalog):
        for line in self.translation._catalog[''].split('\n'):
            if line.startswith('Plural-Forms:'):
                return line.split(':', 1)[1].strip()
    return None
