using recursive function in python to find end-to-end lineage in a data frame

Question

all. I have this data frame with two columns: source and target.

source	target
a	c
b	c
z	v
e	a
f	a
g	b
h	g
i	g
j	i
x	k
y	z

for target "c", it has two sources: "a" and "b", then for "a", it has two sources: "e" and "f", etc.

I would like to use a recursive function to find all lineages starting from "c". The expected outcome should be:

source	target
a	c
b	c
e	a
f	a
g	b
h	g
i	g
j	i

Any help would be appreciated!

I have tried to use for loop in side a recursive function, however it didn't do the job i expected.