#include<bits/stdc++.h>
#include<sstream>
#include<cassert>
#define fi first
#define se second
#define i128 __int128
using namespace std;
typedef long long ll;
typedef double db;
typedef pair<int,int> PII;
const double eps=1e-7;
const int N=5e5+7 ,M=5e5+7, INF=0x3f3f3f3f,mod=1e9+7,mod1=998244353;
const long long int llINF=0x3f3f3f3f3f3f3f3f;
inline ll read() {ll x=0,f=1;char c=getchar();while(c<'0'||c>'9') {if(c=='-') f=-1;c=getchar();}
while(c>='0'&&c<='9') {x=(ll)x*10+c-'0';c=getchar();} return x*f;}
inline void write(ll x) {if(x < 0) {putchar('-'); x = -x;}if(x >= 10) write(x / 10);putchar(x % 10 + '0');}
inline void write(ll x,char ch) {write(x);putchar(ch);}
void stin() {freopen("in_put.txt","r",stdin);freopen("my_out_put.txt","w",stdout);}
bool cmp0(int a,int b) {return a>b;}
template<typename T> T gcd(T a,T b) {return b==0?a:gcd(b,a%b);}
template<typename T> T lcm(T a,T b) {return a*b/gcd(a,b);}
void hack() {printf("\n----------------------------------\n");}

int T,hackT;
int n,m,k;
int h[N],e[M],ne[M],w[M],idx;
int f[N];
bool st[N];
int stk[N];

int find(int x) {
	if(x!=f[x]) f[x]=find(f[x]);
	return f[x];
}

void add(int a,int b,int c) {
	e[idx]=b,ne[idx]=h[a],w[idx]=c,h[a]=idx++;
}

void dfs(int u,int fa,int id,vector<int> &vis) {
	if(st[u]) {
		for(int i=1;i<id;i++) vis.push_back(stk[i]);
		return;
	}
	st[u]=true;
	
	int t=1;
	for(int i=h[u];i!=-1;i=ne[i]) {
		int j=e[i];
		
		if(j==fa&&t==1) {
			t--;
			continue;
		}
		
		stk[id]=w[i];
		dfs(j,u,id+1,vis);
		if(vis.size()!=0) return ;
	}
	
	st[u]=false;
}

void solve() {
	n=read(),m=read();
	
	memset(h,-1,sizeof(int)*(n+4));
	idx=0;
	for(int i=1;i<=n;i++) f[i]=i;
	
	bool flag=false;
	vector<int> vis;
	for(int i=1;i<=m;i++) {
		int a=read(),b=read();
		int fa=find(a),fb=find(b);
		
		if(flag) continue;
		add(a,b,i),add(b,a,i);
		if(fa!=fb) {
			f[fa]=fb;
		}else {
			memset(st,false,sizeof(bool)*(n+4));
			flag=true;
			dfs(a,-1,1,vis);
		}
	}
	
	if(!flag) printf("-1\n");
	else {
		sort(vis.begin(),vis.end());
		for(auto &it:vis) printf("%d ",it);
		printf("\n");
	}
}   

int main() {
    // init();
    // stin();
	// ios::sync_with_stdio(false); 

    scanf("%d",&T);
    // T=1; 
    while(T--) hackT++,solve();
    
    return 0;       
}