// MagicDark
#include <bits/stdc++.h>
#define debug cerr << "\33[32m[" << __LINE__ << "]\33[m "
#define SZ(x) ((int) x.size() - 1)
#define all(x) x.begin(), x.end()
#define ms(x, y) memset(x, y, sizeof x)
#define F(i, x, y) for (int i = (x); i <= (y); i++)
#define DF(i, x, y) for (int i = (x); i >= (y); i--)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
template <typename T> T& chkmax(T &x, T y) {return x = max(x, y);}
template <typename T> T& chkmin(T &x, T y) {return x = min(x, y);}
template <typename T> T& read(T &x) {
	x = 0; int f = 1; char c = getchar();
	for (; !isdigit(c); c = getchar()) if (c == '-') f = - f;
	for (; isdigit(c); c = getchar()) x = (x << 1) + (x << 3) + (c ^ 48);
	return x *= f;
}
const int N = 4010, inf = 1e9;
vector <int> v[N];
int id[N][N];
int n, m, dep[N], p[N], cnt[N], vv[N], vw[N], dfn[N], rdfn[N], pcnt, s[N], fa[N];
void dfs(int x, int fa) {
	::fa[x] = fa;
	dfn[x] = ++pcnt;
	dep[x] = dep[fa] + 1;
	for (int i: v[x])
		if (i != fa) {
			if (!dep[i]) {
				dfs(i, x);
				chkmin(vw[x], min(vv[i], vw[i]));
				s[x] += s[i];
			} else if (dep[i] < dep[x]) {
				p[i] = x, p[x] = i;
				cnt[x]++, cnt[i]++;
				chkmin(vv[x], dep[i]);
				s[::fa[i]]--;
				s[x]++;
			}
		}
	rdfn[x] = pcnt;
}
void zhk() {
	read(n), read(m);
	F(i, 1, n) v[i].clear();
	F(i, 1, m) {
		int x, y; read(x), read(y);
		id[x][y] = id[y][x] = i;
		v[x].push_back(y);
		v[y].push_back(x);
	}
	vector <int> ans;
	auto solve = [&] () -> bool {
		pcnt = 0;
		F(i, 1, n) {
			dep[i] = 0;
			s[i] = 0;
			// p[i] = 0;
			cnt[i] = 0;
			vw[i] = vv[i] = inf;
		}
		F(i, 1, n)
			if (!dep[i]) dfs(i, 0);
		F(i, 1, n)
			for (int j: v[i]) if (dep[i] > dep[j]) {
				if (abs(dep[i] - dep[j]) == 1) {
					if (cnt[i] > 1) continue;
					if (cnt[i] == 1) {
						if (dep[p[i]] > dep[i]) continue;
						if (vw[i] <= dep[p[i]]) continue;
					}
					if (cnt[j] > 1) continue;
					if (cnt[j] == 1) {
						if (!(dfn[i] <= dfn[p[j]] && dfn[p[j]] <= rdfn[i])) continue;
						if (vw[p[j]] <= dep[j] || vv[p[j]] < dep[j]) continue;
					}
					// ans.push_back(id[i][j]);
					// v[i].erase(find(all(v[i]), j));
					// v[j].erase(find(all(v[j]), i));
					// return true;
				} else {
					if (s[i] > 1 || s[j] > 1) continue;
				}
				ans.push_back(id[i][j]);
				v[i].erase(find(all(v[i]), j));
				v[j].erase(find(all(v[j]), i));
				return true;
			}
		return false;
	};
	F(i, 1, m) {
		if (!solve()) {
			puts("-1");
			return;
		}
	}
	reverse(all(ans));
	for (int i: ans) cout << i << ' '; cout << '\n';
}
signed main() {
	int _ = 1;
	cin >> _;
	while (_--) zhk();
	return 0;
}
/* why?
*/