Get the prefix with id 'id'.

def get(cls, id):
        """ Get the prefix with id 'id'.
        """

        # cached?
        if CACHE:
            if id in _cache['Prefix']:
                log.debug('cache hit for prefix %d' % id)
                return _cache['Prefix'][id]
            log.debug('cache miss for prefix %d' % id)

        try:
            prefix = Prefix.list({'id': id})[0]
        except IndexError:
            raise NipapNonExistentError('no prefix with ID ' + str(id) + ' found')

        _cache['Prefix'][id] = prefix
        return prefix