def solve():
    n = int(input())
    a = [tuple(map(int, input().split())) for i in range(n)]
 
    N = 2 * 10**5 + 5
    p = list(range(N))  
 
    def find(x):
        while x != p[x]:
            p[x] = p[p[x]]
            x = p[x]
        return x
 
    def unite(x, y):
        x = find(x)
        y = find(y)
        if x != y:
            p[y] = x
            return True
        return False
 
    s_indices = []
    sintervals = []
 
    for i in range(n):
        u, v = a[i]
        if unite(u, v):
            s_indices.append(i + 1)
            sintervals.append((min(u, v), max(u, v)))
 
    print(len(s_indices))
    print(*s_indices)
 
t=int(input())
for i in range(t):
	solve()
 

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2
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4
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