'Validate the given disk type in extra_spec.
This method throws ImageUnacceptable if the disk type is not a
supported one.
:param extra_spec_disk_type: disk type
:raises: ImageUnacceptable'

@staticmethod
def validate(extra_spec_disk_type):

    if (not ImageDiskType.is_valid(extra_spec_disk_type)):
        raise exception.ImageUnacceptable((_('Invalid    disk    type:    %s.') % extra_spec_disk_type))
