#include<bits/stdc++.h>
using namespace std;
#define N 200010
#define int long long
int n,m,k,deg[N],d[N],f[N];
int p1,p2;
map<pair<int,int>,int> mp;
struct edge{
	int u,v;
}a[N];
vector<vector<int>> g;
vector<vector<int>> ans;
int vis[N],ch;
int cmp(edge x,edge y)
{
	return x.u<y.u||x.u==y.u&&x.v<y.v;
}
void dfs(int u)
{
	if(ch) return;
	if(u==p2)
	{
		ch=1;
		vector<int> ans1;
		int x=p2;
		while(x!=p1)
		{
			ans1.push_back(x);
			mp[{x,f[x]}]--;
			mp[{f[x],x}]--;
			x=f[x];
		}
		ans1.push_back(p1);
		ans.push_back(ans1);
		return;
	}
	for(auto v:g[u])
	{
		if(vis[v]) continue;
		if(mp[{u,v}]==0) continue;
//		for(int i=1;i<=mp[{u,v}];i++)
		{
			f[v]=u;
			vis[u]=1;
			dfs(v);
			vis[u]=0;
		}
	}
}
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	int T;
	cin>>T;
	while(T--)
	{
		cin>>n>>m;
		g.resize(n+1);
		g.clear();
		mp.clear();
		ans.clear();
		for(int i=1;i<=n;i++)
		{
			d[i]=deg[i]=vis[i]=0;
		}
		if(m%(n-1)==0) k=m/(n-1);
		else k=m/(n-1)+1;
		for(int i=1;i<=m;i++)
		{
			cin>>a[i].u>>a[i].v;
			if(a[i].u>a[i].v) swap(a[i].u,a[i].v);
		}
		if(m==1)
		{
			cout<<a[1].u<<" "<<a[1].v<<"\n";
			cout<<"2 "<<a[1].u<<" "<<a[1].v<<"\n";
			continue;
		}
		sort(a+1,a+m+1,cmp);
		int x1=0,x2=0;
		for(int i=1;i<=m;i++)
		{
			deg[a[i].u]++;deg[a[i].v]++;
			if(a[i].u==a[i-1].u&&a[i].v==a[i-1].v)
			{
				mp[{a[i].u,a[i].v}]++;mp[{a[i].v,a[i].u}]++;
				if(mp[{a[i].u,a[i].v}]>=k)
				{
					x1=a[i].u;
					x2=a[i].v;
				}
				continue;
			}
			g[a[i].u].push_back(a[i].v);
			g[a[i].v].push_back(a[i].u);
			mp[{a[i].u,a[i].v}]=mp[{a[i].v,a[i].u}]=1;
		}
		if(x1)
		{
			cout<<x1<<" "<<x2<<"\n";
			for(int i=1;i<=k;i++)
			{
				cout<<"2 "<<x1<<" "<<x2<<"\n";
			}
			continue;
		}
		queue<int> q;
		for(int i=1;i<=n;i++)
		{
			d[i]=g[i].size();
			if(g[i].size()==1)
			{
				q.push(i);
				continue;
			}
		}
		while(q.size())
		{
			int u=q.front();q.pop();
			vis[u]=1;
			for(auto v:g[u])
			{
				if(vis[v]) continue;
				deg[v]=deg[v]-mp[{u,v}];
				d[v]--;
				if(d[v]==1) q.push(v);
				break;
			}
		}
		int mx=0;
		p1=p2=0;
		for(int i=1;i<=n;i++)
		{
			if(vis[i]) continue;
			if(deg[i]>mx)
			{
				mx=deg[i];
				p1=i;
			}
		}
		mx=0;
		for(int i=1;i<=n;i++)
		{
			if(vis[i]) continue;
			if(deg[i]>mx&&i!=p1)
			{
				mx=deg[i];
				p2=i;
			}
		}
//		cout<<p1<<" "<<p2<<"\n";
//		for(int i=1;i<=n;i++)
//		{
//			for(int j=1;j<=n;j++)
//			{
//				
//				cout<<mp[{i,j}]<<" ";
//			}
//			cout<<"\n";
//		}
		for(int i=1;i<=k;i++)
		{
			ch=0;
			dfs(p1);
		}
		if(ans.size()<k)
		{
			cout<<"-1\n";
			continue;
		}
		cout<<p1<<" "<<p2<<"\n";
		for(int i=0;i<ans.size();i++)
		{
			cout<<ans[i].size();
			for(int j=ans[i].size()-1;j>=0;j--) cout<<" "<<ans[i][j];
			cout<<"\n";
		}
	}
	return 0;
}