#include <iostream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstdlib>
#include <cassert>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <bitset>
#include <string>
#include <algorithm>
#include <utility>
#define llint long long
#define inf 1e18
#define rep(x, s, t) for(llint (x) = (s); (x) < (t); (x)++)
#define Rep(x, s, t) for(llint (x) = (s); (x) <= (t); (x)++)
#define chmin(x, y) (x) = min((x), (y))
#define chmax(x, y) (x) = max((x), (y))
#define mod 1000000007

using namespace std;
typedef pair<llint, llint> P;

llint n, k;
vector<llint> G[1005];


typedef pair<llint, llint> P;

int parent[1005];
llint dp[1005][1005], dp2[1005][1005];
llint sum[1005][1005], sum2[1005][1005];

llint get(int u, int v, int x)
{
	if(parent[u] == v) return dp2[u][x];
	else return dp[v][x];
}
llint getsum(int u, int v, int x)
{
	if(parent[u] == v) return sum2[u][x];
	else return sum[v][x];
}

void dfs(int v, int p)
{
	parent[v] = p;
	for(int i = 0; i < G[v].size(); i++){
		if(G[v][i] == p) continue;
		dfs(G[v][i], v);
	}
	
	for(int j = 1; j <= k; j++){
		llint mul = 1;
		for(int i = 0; i < G[v].size(); i++){
			int u = G[v][i];
			if(u == p) continue;
			mul *= getsum(v, u, j), mul %= mod;
		}
		dp[v][j] = mul;
		sum[v][j] = sum[v][j-1] + dp[v][j], sum[v][j] %= mod;
	}
}

llint lsum[1005], rsum[1005];
void dfs2(int v, int p)
{
	llint m = G[v].size(), mul;
	
	for(int j = 1; j <= k; j++){
		mul = lsum[0] = 1;
		for(int i = 0; i < m; i++){
			int u = G[v][i];
			mul *= getsum(v, u, j), mul %= mod; //
			lsum[i+1] = mul;
		}
		mul = rsum[m+1] = 1;
		for(int i = m-1; i >= 0; i--){
			int u = G[v][i];
			mul *= getsum(v, u, j), mul %= mod; //
			rsum[i+1] = mul;
		}
		for(int i = 0; i < m; i++){
			int u = G[v][i];
			if(u == p) continue;
			dp2[u][j] = lsum[i] * rsum[i+2] % mod;
			sum2[u][j] = (sum2[u][j-1] + dp2[u][j]) % mod;
		}
	}
	for(int i = 0; i < G[v].size(); i++){
		if(G[v][i] == p) continue;
		dfs2(G[v][i], v);
	}
}

int size[1005];
bool used[1005];

int sizedfs(int v, int pre)
{
	int ret = 1;
	for(int i = 0; i < G[v].size(); i++){
		if(G[v][i] == pre) continue;
		if(used[G[v][i]]) continue;
		ret += sizedfs(G[v][i], v);
	}
	return size[v] = ret;
}

int centdfs(int v, int pre, int sz)
{
	for(int i = 0; i < G[v].size(); i++){
		if(G[v][i] == pre) continue;
		if(used[G[v][i]]) continue;
		if(size[G[v][i]] > sz/2) return centdfs(G[v][i], v, sz);
	}
	return v;
}

llint calcdfs(llint v, llint p, llint k)
{
	llint ret = 0;
	if(p != -1) ret = getsum(p, v, k-1);
	
	llint mul = 1;
	for(int i = 0; i < G[v].size(); i++){
		llint u = G[v][i];
		if(u == p) continue;
		if(used[u]){
			mul *= getsum(v, u, k-1), mul %= mod;
			continue;
		}
		mul *= calcdfs(G[v][i], v, k), mul %= mod;
	}
	ret += mul, ret %= mod;
	return ret;
}

llint ans = 0;
void solve(int v)
{
	sizedfs(v, -1);
	v = centdfs(v, -1, size[v]);
	
	/* 処理  */
	for(int i = 2; i <= k; i++){
		ans += calcdfs(v, -1, i);
		ans %= mod;
	}
	
	used[v] = true;
	for(int i = 0; i < G[v].size(); i++){
		if(used[G[v][i]]) continue;
		solve(G[v][i]);
	}
}

int main(void)
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> n >> k;
	llint u, v;
	for(int i = 1; i <= n-1; i++){
		cin >> u >> v;
		G[u].push_back(v);
		G[v].push_back(u);
	}
	if(k == 1){
		cout << 1 << endl;
		return 0;
	}
	
	dfs(1, -1);
	dfs2(1, -1);
	
	/*for(int i = 1; i <= n; i++){
		for(int j = 0; j < G[i].size(); j++){
			cout << i << " " << G[i][j] << " : ";
			for(int l = 1; l <= k; l++){
				cout << get(i, G[i][j], l) << " ";
			}
			cout << endl;
		}
	}*/
	
	solve(1);
	ans += 1, ans %= mod;
	cout << ans << endl;
	
	return 0;
}