#include <iostream>
#include <queue>
#include <stack>
#include <vector>
#include <deque>
#include <set>
#include <map>
#include <unordered_map>
#include <cassert>
#include <algorithm>
#include <cmath>
#include <random>
#include <ctime>
#include <cstdlib>
#include <chrono>

using namespace std;

const int DIM = 4005;

int viz[DIM], gr[DIM], h[DIM], low[DIM];
vector<pair<int, int>> e;
vector<pair<int, int>> v[DIM];
vector<int> bad;

void dfs(int nod, int papa = 0) {
  viz[nod] = 1;
  for (auto [it, i] : v[nod]) {
    if (it == papa)
      continue;

    if (viz[it] == 0) {
      low[it] = h[it] = h[nod] + 1;
      dfs(it, nod);
      if (low[it] == h[it]) {
        bad.push_back(i);
      }
    }

    low[nod] = min(low[nod], low[it]);
  }
}

void remove_edge(int i) {
  int x, y;
  tie(x, y) = e[i];
  v[x].erase(find(v[x].begin(), v[x].end(), make_pair(y, i)));
  v[y].erase(find(v[y].begin(), v[y].end(), make_pair(x, i)));
}

void solve() {
  int n, m;
  cin >> n >> m;

  e.resize(m + 1);
  for (int i = 1; i <= n; ++i) {
    v[i].clear();
  }
  for (int i = 1; i <= m; ++i) {
    int x, y;
    cin >> x >> y;
    e[i] = {x, y};
    v[x].push_back({y, i});
    v[y].push_back({x, i});
  }

  int st = 0, dr = m - 1;
  vector<int> ans(m);
  while (1) {
    bad.clear();
    for (int i = 1; i <= n; ++i)
      viz[i] = low[i] = h[i] = 0;

    for (int i = 1; i <= n; ++i) {
      if (!viz[i])
        dfs(i);
    }

    bool ok = false;
    for (auto it : bad) {
      ok = true;
      ans[st++] = it;
      remove_edge(it);
    }

    for (int i = 1; i <= n; ++i) {
      if (v[i].size() <= 2) {
        for (auto [it, j] : v[i]) {
          if (v[it].size() <= 2) {
            ok = true;
            ans[dr--] = j;
            remove_edge(j);
            break;
          }
        }
      }
    }

    if (!ok)
      break;
  }

  if (st > dr) {
    for (auto it : ans)
      cout << it << " ";
  } else {
    cout << "-1";
  }
  cout << "\n";
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);

  int t = 1;
  cin >> t;
  while (t--)
    solve();

  return 0;
}