using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[] NMi => ReadLine().Split().Select(c => int.Parse(c) - 1).ToArray();
    static int[][] NMap(int n) => Enumerable.Repeat(0, n).Select(_ => NMi).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, k) = (c[0], c[1]);
        if (k <= 3)
        {
            WriteLine(0);
            return;
        }
        var map = NMap(n - 1);
        var tree = new List<int>[n];
        for (var i = 0; i < n; ++i) tree[i] = new List<int>();
        foreach (var edge in map)
        {
            tree[edge[0]].Add(edge[1]);
            tree[edge[1]].Add(edge[0]);
        }
        var ans = 0L;
        if (k > 6 * n + 10)
        {
            var (s, m, l) = DFS1(0, -1, tree, k);
            ans = m;
            for (var i = 0; i < s.Length; ++i) ans += s[i];
            for (var i = 0; i < l.Length; ++i) ans += l[i];
        }
        else
        {
            var list = DFS2(0, -1, tree, k);
            for (var i = 0; i < list.Length; ++i) ans += list[i];
        }
        WriteLine(ans % mod);
    }
    static int mod = 1_000_000_007;
    static (long[] small, long mid, long[] large) DFS1(int cur, int prev, List<int>[] tree, int k)
    {
        var small = new long[3 * k + 1];
        var mid = 0L;
        var large = new long[3 * k + 1];
        for (var i = 0; i < small.Length; ++i) small[i] = 1;
        mid = 1;
        for (var i = 0; i < large.Length; ++i) large[i] = 1;
        if (prev >= 0 && tree[cur].Count == 1)
        {
            return (small, mid, large);
        }
        foreach (var next in tree[cur])
        {
            if (prev == next) continue;
            var (ns, nm, nl) = DFS1(next, cur, tree, k);
            for (var i = 0; i < small.Length; ++i)
            {
                if (i < 3)
                {
                    small[i] = small[i] * ns[i + 3] % mod;
                    large[i] = large[i] * ns[i + 3] % mod;
                }
                else if (i + 3 > small.Length)
                {
                    small[i] = small[i] * ((ns[i - 3] + nm) % mod) % mod;
                    large[i] = large[i] * ((ns[i - 3] + nm) % mod) % mod;
                }
                else
                {
                    small[i] = small[i] * ((ns[i - 3] + ns[i + 3]) % mod) % mod;
                    large[i] = large[i] * ((nl[i - 3] + nl[i + 3]) % mod) % mod;
                }
                mid = mid * nm % mod * 2 % mod;
            }
        }
        return (small, mid, large);
    }
    static long[] DFS2(int cur, int prev, List<int>[] tree, int k)
    {
        var ans = new long[k];
        for (var i = 0; i < k; ++i) ans[i] = 1;
        if (prev >= 0 && tree[cur].Count == 1)
        {
            return ans;
        }
        foreach (var next in tree[cur])
        {
            if (prev == next) continue;
            var nans = DFS2(next, cur, tree, k);
            for (var i = 0; i < k; ++i)
            {
                if (i - 3 >= 0 && i + 3 < k)
                {
                    ans[i] = ans[i] * ((nans[i - 3] + nans[i + 3]) % mod) % mod;
                }
                else if (i - 3 >= 0)
                {
                    ans[i] = ans[i] * nans[i - 3] % mod;
                }
                else if (i + 3 < k)
                {
                    ans[i] = ans[i] * nans[i + 3] % mod;
                }
                else
                {
                    ans[i] = 0;
                }
            }
        }
        return ans;
    }
}