#include <bits/stdc++.h>
using namespace std;
long long MOD = 1000000007;
vector<int> parent(vector<vector<int>> &E, int r){
	int N = E.size();
	vector<int> p(N, -1);
	queue<int> Q;
	Q.push(r);
	while (!Q.empty()){
		int v = Q.front();
		Q.pop();
		for (int w : E[v]){
			if (p[w] == -1){
				p[w] = v;
				Q.push(w);
			}
		}
	}
	return p;
}
vector<vector<int>> child(vector<vector<int>> E, int r){
	int N = E.size();
	vector<vector<int>> c(N);
	queue<int> Q;
	Q.push(r);
	while (!Q.empty()){
		int v = Q.front();
		Q.pop();
		for (int w : E[v]){
			if (c[w].empty()){
				c[v].push_back(w);
				Q.push(w);
			}
		}
	}
	return c;
}
void dfs1(vector<vector<long long>> &dp1, vector<vector<int>> &c, int K, int v){
  for (int i = 0; i < K; i++){
    dp1[v][i] = 1;
  }
  for (int w : c[v]){
    dfs1(dp1, c, K, w);
    for (int i = 0; i < K; i++){
      dp1[v][i] *= dp1[w][i];
      dp1[v][i] %= MOD;
    }
  }
  for (int i = 1; i < K; i++){
    dp1[v][i] += dp1[v][i - 1];
    dp1[v][i] %= MOD;
  }
  return;
}
void dfs2(vector<vector<long long>> &dp1, vector<vector<long long>> &dp2, vector<vector<int>> &c, int K, int v){
  int deg = c[v].size();
  vector<vector<long long>> L(deg + 1, vector<long long>(K, 1));
  for (int i = 0; i < deg; i++){
    L[0][0] = 0;
    for (int j = 0; j < K; j++){
      L[i + 1][j] = L[i][j] * dp1[c[v][i]][j] % MOD;
    }
  }
  vector<vector<long long>> R(deg + 1, vector<long long>(K, 1));
  for (int i = deg - 1; i >= 0; i--){
    R[i][0] = 0;
    for (int j = 0; j < K; j++){
      R[i][j] = R[i + 1][j] * dp1[c[v][i]][j] % MOD;
    }
  }
  for (int i = 0; i < deg; i++){
    for (int j = 0; j < K; j++){
      dp2[c[v][i]][j] = L[i][j] * R[i + 1][j] % MOD * dp1[v][j] % MOD;
      dfs2(dp1, dp2, c, K, c[v][i]);
    }
  }
  return;
}
int main(){
  int N, K;
  cin >> N >> K;
  vector<vector<int>> E(N);
  for (int i = 0; i < N - 1; i++){
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    E[a].push_back(b);
    E[b].push_back(a);
  }
  vector<int> p = parent(E, 0);
  vector<vector<int>> c = child(E, 0);
  vector<vector<long long>> dp1(N, vector<long long>(K, 1));
  dfs1(dp1, c, K, 0);
  /*
  for (int i = 0; i < N; i++){
    cout << "i = " << i << endl;
    for (int j = 0; j < K; j++){
      cout << dp1[i][j] << ' ';
    }
    cout << endl;
  }
  */
  vector<vector<long long>> dp2(N, vector<long long>(K, 1));
  dfs2(dp1, dp2, c, K, 0);
  long long ans = 0;
  for (int i = 0; i < N; i++){
    ans += dp1[i][K - 1] * dp2[i][K - 1] % MOD;
    ans %= MOD;
  }
  cout << ans << endl;
}