'Validate the given disk type in extra_spec.
This method throws an instance of InvalidDiskTypeException if the given
disk type is invalid.
:param extra_spec_disk_type: disk type in extra_spec
:raises: InvalidDiskTypeException'

@staticmethod
def validate(extra_spec_disk_type):

    if (not VirtualDiskType.is_valid(extra_spec_disk_type)):
        raise vmdk_exceptions.InvalidDiskTypeException(disk_type=extra_spec_disk_type)
