Issue with Automatic partitioning on partitioned disks

[Armin ranjbar <zoup@zoup.org>]

by using this preseed file 

d-i partman-auto/init_automatically_partition select Guided - use the
largest continuous free space d-i partman-auto/disk
string /dev/discs/disc0/disc d-i partman-auto/method string lvm
d-i partman-auto/purge_lvm_from_device boolean true
d-i partman-lvm/confirm boolean true
d-i partman-auto/choose_recipe select All files in one partition
(recommended for new users)

its very ok when the disk has no partition available , but when there are
partition available ( old linux installation ) it does not automatically
partition the partitions , any idea  how can i force automatic
partitioning even on partitioned disks ?
 
-- 
Armin ranjbar , System Administrator