#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> PII;

const int N = 4005;

int n, m;
vector<PII> e, opt;
int g[N][N];
int la[N], ne[N * 2], en[N * 2], idx;
int dfn[N], low[N], dfst;
int sta[N], tt, tte;
PII stae[N];
int dcc_cnt;
vector<int> dcc[N];
vector<PII> dcce[N], bridge;
int deg[N];

inline void Add(int a, int b)
{
    ne[ ++ idx] = la[a];
    la[a] = idx;
    en[idx] = b;
}
inline void Tarjan(int u, int fr)
{
    dfn[u] = low[u] = ++ dfst;
    sta[ ++ tt] = u;
    for(int i = la[u]; i; i = ne[i])
    {
        int v = en[i];
        if(!dfn[v])
        {
            stae[ ++ tte] = {u, v};
            Tarjan(v, i);
            low[u] = min(low[u], low[v]);
            if(low[v] > dfn[u])
            {
                bridge.push_back(stae[tte -- ]);
            }
        }
        else if(i != (fr ^ 1) && dfn[v] < dfn[u])
        {
            low[u] = min(low[u], dfn[v]);
            stae[ ++ tte] = {v, u};
        }
    }
    if(low[u] == dfn[u])
    {
        dcc_cnt ++ ;
        dcc[dcc_cnt].clear();
        dcce[dcc_cnt].clear();
        int v = 0;
        do{
            v = sta[tt -- ];
            dcc[dcc_cnt].push_back(v);
        }while(v != u);
        while(dfn[stae[tte].first] >= dfn[u])
        {
            dcce[dcc_cnt].push_back(stae[tte -- ]);
        }
        if(dcce[dcc_cnt].empty()) dcc_cnt -- ;
    }
}

inline bool WorkDCC(vector<int> p, vector<PII> e);
inline bool WorkGraph(vector<int> p, vector<PII> e)
{
    if(e.empty()) return 1;
    for(int i : p) dfn[i] = la[i] = 0;
    idx = 1, dfst = 0;
    int st = dcc_cnt + 1;
    bridge.clear();
    for(PII &i : e) Add(i.first, i.second), Add(i.second, i.first);
    for(int i : p) if(!dfn[i]) Tarjan(i, 0);
    for(PII &i : bridge) opt.emplace_back(i);
    int ed = dcc_cnt;
    for(int i = st; i <= ed; i ++ ) if(!WorkDCC(dcc[i], dcce[i])) return 0;
    return 1;
}
inline bool WorkDCC(vector<int> p, vector<PII> e)
{
    if(e.empty()) return 1;
    vector<PII> e0;
    PII e1(-1, -1);
    for(int i : p) deg[i] = 0;
    for(PII &i : e) deg[i.first] ++ , deg[i.second] ++ ;
    for(PII &i : e) if(deg[i.first] == 2 && deg[i.second] == 2) e1 = i;
    // puts("#");
    // for(int i : p) printf("%d ", i);
    // puts("");
    // for(PII &i : e) printf("(%d %d) ", i.first, i.second);
    // puts("");
    if(e1.first == -1) return 0;
    for(PII &i : e) if(i != e1) e0.push_back(i);
    if(!WorkGraph(p, e0)) return 0;
    opt.push_back(e1);
    return 1;
}

inline void Solve()
{
    scanf("%d%d", &n, &m);
    e.resize(m);
    for(int i = 0; i < m; i ++ )
    {
        scanf("%d%d", &e[i].first, &e[i].second);
        g[e[i].first][e[i].second] = g[e[i].second][e[i].first] = i + 1;
    }
    vector<int> p;
    for(int i = 1; i <= n; i ++ ) p.push_back(i);
    if(!WorkGraph(p, e)) puts("-1");
    else
    {
        for(PII &i : opt) printf("%d ", g[i.first][i.second]);
        puts("");
    }
    opt.clear();
    dcc_cnt = 0;
    for(PII &i : e) g[i.first][i.second] = g[i.second][i.first] = 0;
    e.clear();
}

int main()
{
    int T;
    scanf("%d", &T);
    while(T -- ) Solve();
    return 0;
}