#line 1 "main.cpp"
#include <bits/stdc++.h>
#line 2 "/home/user/GitHub/competitive-programming-library/utils/macros.hpp"
#define REP(i, n) for (int i = 0; (i) < (int)(n); ++ (i))
#define REP3(i, m, n) for (int i = (m); (i) < (int)(n); ++ (i))
#define REP_R(i, n) for (int i = (int)(n) - 1; (i) >= 0; -- (i))
#define REP3R(i, m, n) for (int i = (int)(n) - 1; (i) >= (int)(m); -- (i))
#define ALL(x) std::begin(x), std::end(x)
#line 3 "/home/user/GitHub/competitive-programming-library/modulus/modpow.hpp"

inline int32_t modpow(uint_fast64_t x, uint64_t k, int32_t MOD) {
    assert (/* 0 <= x and */ x < (uint_fast64_t)MOD);
    uint_fast64_t y = 1;
    for (; k; k >>= 1) {
        if (k & 1) (y *= x) %= MOD;
        (x *= x) %= MOD;
    }
    assert (/* 0 <= y and */ y < (uint_fast64_t)MOD);
    return y;
}
#line 4 "/home/user/GitHub/competitive-programming-library/modulus/modinv.hpp"

inline int32_t modinv_nocheck(int32_t value, int32_t MOD) {
    assert (0 <= value and value < MOD);
    if (value == 0) return -1;
    int64_t a = value, b = MOD;
    int64_t x = 0, y = 1;
    for (int64_t u = 1, v = 0; a; ) {
        int64_t q = b / a;
        x -= q * u; std::swap(x, u);
        y -= q * v; std::swap(y, v);
        b -= q * a; std::swap(b, a);
    }
    if (not (value * x + MOD * y == b and b == 1)) return -1;
    if (x < 0) x += MOD;
    assert (0 <= x and x < MOD);
    return x;
}

inline int32_t modinv(int32_t x, int32_t MOD) {
    int32_t y = modinv_nocheck(x, MOD);
    assert (y != -1);
    return y;
}
#line 7 "/home/user/GitHub/competitive-programming-library/modulus/mint.hpp"


/**
 * @brief quotient ring / 剰余環 $\mathbb{Z}/n\mathbb{Z}$
 */
template <int32_t MOD>
struct mint {
    int32_t value;
    mint() : value() {}
    mint(int64_t value_) : value(value_ < 0 ? value_ % MOD + MOD : value_ >= MOD ? value_ % MOD : value_) {}
    mint(int32_t value_, std::nullptr_t) : value(value_) {}
    explicit operator bool() const { return value; }
    inline mint<MOD> operator + (mint<MOD> other) const { return mint<MOD>(*this) += other; }
    inline mint<MOD> operator - (mint<MOD> other) const { return mint<MOD>(*this) -= other; }
    inline mint<MOD> operator * (mint<MOD> other) const { return mint<MOD>(*this) *= other; }
    inline mint<MOD> & operator += (mint<MOD> other) { this->value += other.value; if (this->value >= MOD) this->value -= MOD; return *this; }
    inline mint<MOD> & operator -= (mint<MOD> other) { this->value -= other.value; if (this->value <    0) this->value += MOD; return *this; }
    inline mint<MOD> & operator *= (mint<MOD> other) { this->value = (uint_fast64_t)this->value * other.value % MOD; return *this; }
    inline mint<MOD> operator - () const { return mint<MOD>(this->value ? MOD - this->value : 0, nullptr); }
    inline mint<MOD> pow(uint64_t k) const { return mint<MOD>(modpow(value, k, MOD), nullptr); }
    inline mint<MOD> inv() const { return mint<MOD>(modinv(value, MOD), nullptr); }
    inline mint<MOD> operator /  (mint<MOD> other) const { return *this *  other.inv(); }
    inline mint<MOD> operator /= (mint<MOD> other)       { return *this *= other.inv(); }
    inline bool operator == (mint<MOD> other) const { return value == other.value; }
    inline bool operator != (mint<MOD> other) const { return value != other.value; }
};
template <int32_t MOD> mint<MOD> operator * (int64_t value, mint<MOD> n) { return mint<MOD>(value) * n; }
template <int32_t MOD> std::istream & operator >> (std::istream & in, mint<MOD> & n) { int64_t value; in >> value; n = value; return in; }
template <int32_t MOD> std::ostream & operator << (std::ostream & out, mint<MOD> n) { return out << n.value; }
#line 4 "main.cpp"
using namespace std;

constexpr int MOD = 1000000007;
mint<MOD> solve(int n, int k, const vector<vector<int> > & g) {
    map<pair<int, int>, vector<mint<MOD> > > memo;
    auto go1 = [&](auto && go1, int x, int parent) -> const vector<mint<MOD> > & {
        auto key = make_pair(x, parent);
        if (memo.count(key)) return memo[key];

        vector<mint<MOD> > dp(k, 1);
        for (int y : g[x]) if (y != parent) {
            auto sub = go1(go1, y, x);
            mint<MOD> acc = 0;
            REP (i, k) {
                acc += sub[i];
                dp[i] *= acc;
            }
        }
        return memo[key] = dp;
    };
    REP (root, n) {
        go1(go1, root, -1);
    }

    auto go2 = [&](auto && go2, int x, int parent, int root) -> vector<mint<MOD> > {
        vector<mint<MOD> > dp(k, 1);
        for (int y : g[x]) if (y != parent) {
            const auto & sub1 = go1(go1, y, x);
            auto sub2 = go2(go2, y, x, root);
            mint<MOD> acc = 0;
            REP (i, k) {
                dp[i] *= acc + (y < root ? 0 : sub2[i]);
                acc += sub1[i];
            }
        }
        return dp;
    };

    mint<MOD> ans = 0;
    REP (root, n) {
        auto dp = go2(go2, root, -1, root);
        ans += accumulate(ALL(dp), mint<MOD>());
    }
    return ans;
}

// generated by online-judge-template-generator v4.1.1 (https://github.com/kmyk/online-judge-template-generator)
int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    constexpr char endl = '\n';
    int n; cin >> n;
    int k; cin >> k;
    vector<vector<int> > g(n);
    REP (i, n - 1) {
        int a, b; cin >> a >> b;
        -- a;
        -- b;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    auto ans = solve(n, k, g);
    cout << ans << endl;
    return 0;
}