[Python] Merging multiple rows of data based Parent Child relationship

I would like to know the code to merge cells which has a parent and child relationship based on dash lines "-" as condition.

The relationship

1. Parent "A" will not have any dash lines
2. Immediate Child "B" will have a a single dash line "A - B"
3. "C" is the Child of "B" , will have two dash lines "A - B -- C"

Dash lines decide the parent child relationship. There is a single space between dash line and the parent and child i.e A - B -- C

Please see the below table. I would like build an column named MERGED DATA from the ORIGINAL DATA column .

Please note the "Powdered Cheese" will find the parent as "Milk" and not "Fish" .

SL No ORIGINAL DATA MERGED DATA
1 FISH FISH
2 - Salmon FISH - Salmon
3 -- Trout FISH - Salmon -- Trout
4 Milk Milk
5 - Milk Powder Milk - Milk Powder
6 - Yoghurt Milk - Yoghurt
7 - Cheese Milk - Cheese
8 -- Powdered Cheese Milk - Cheese -- Powdered Cheese

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