No data passed in: please paste text from data scructure ToString here
for a single or double liked list 

it must be in a format like 

head: 0x7ffd8e677e90
tail: 0x7ffd8e677ea8
node:0x7ffd8e677e90 data:50 prev:0 next: 0x204d490
node:0x204d490 data:49 prev:0x7ffd8e677e90 next:0x204d410
node:0x204d410 data:70 prev:0x204d490 next:0x204d190
node:0x204d190 data:60 prev:0x204d410 next:0x204d110
node:0x204d110 data:40 prev:0x204d190 next:0x7ffd8e677ea8
node:0x7ffd8e677ea8 data:30 prev:0x204d110 next:0

or 

head:0x1e7c690
node:0x1e7c690 data:88 next:0x1e7c610
node:0x1e7c610 data:99 next:0x1e7c590
node:0x1e7c590 data:22 next:0x1e7c510
node:0x1e7c510 data:66 next:0x1e7c4b0
node:0x1e7c4b0 data:33 next:0

node, head, tail, data, next, prev are case sensitive .. 
it needs to exactly match the format and keywords used above.