#include<bits/stdc++.h>
using namespace std;
const int N=1e5+10,M=2e5+10;
int n;
struct node{
    vector<int>e[N];
    int fa[N];
    int find(int x){
        if(x==fa[x])return x;
        return fa[x]=find(fa[x]);
    }
    void init(){
        for(int i=1;i<=n;i++)fa[i]=i,e[i].clear();
    }
    int pd(int x,int y){
        x=find(x);y=find(y);
        if(x^y)return 1;
        return 0;
    }
    void merge(int x,int y){
        if(!pd(x,y))return;
        e[x].push_back(y);e[y].push_back(x);
        fa[find(x)]=find(y);
    }
    int las[N];
    void dfs(int x,int f){
        las[x]=f;
        for(int v:e[x])if(v^f)dfs(v,x);
    }
};
vector<node>T;
void solve(){
    int m;scanf("%d%d",&n,&m);
    T.resize(m/(n-1)+10);
    int tot=1;
    T[tot].init();
    for(int i=1;i<=m;i++){
        int x,y;scanf("%d%d",&x,&y);
        int l=1,r=tot,p=tot+1;
        while(l<=r){
            int mid=l+r>>1;
            if(T[mid].pd(x,y))p=mid,r=mid-1;
            else l=mid+1;
        }
        if(p<=tot)T[p].merge(x,y);
        else tot++,T[tot].init(),T[tot].merge(x,y);
    }
    if(tot!=ceil(1.0*m/(n-1)))printf("-1\n");
    else{
        int x,y;
        for(int i=1;i<=n;i++)if(T[tot].e[i].size()){
            x=i,y=T[tot].e[i].back();
        }
        printf("%d %d\n",x,y);
        for(int i=1;i<=tot;i++){
            T[i].dfs(y,0);
            vector<int>ans;for(int t=x;t!=y;t=T[i].las[t])ans.push_back(t);
            ans.push_back(y);
            printf("%d ",(int)ans.size());
            for(int t:ans)printf("%d ",t);
            printf("\n");
        }
    }
}
int main(){
    int t;scanf("%d",&t);
    while(t--)solve();
    return 0;
}