'Verify vmdk as disk format.
:param disk_format: Disk format of the image'

@staticmethod
def _validate_disk_format(disk_format):

    if (disk_format and (disk_format.lower() != 'vmdk')):
        msg = (_('Cannot    create    image    of    disk    format:    %s.    Only    vmdk    disk    format    is    accepted.') % disk_format)
        LOG.error(msg)
        raise exception.ImageUnacceptable(msg)
