import sys
input = sys.stdin.readline
from collections import deque

mod = 10 ** 9 + 7
N, K = map(int, input().split())
X = [[] for i in range(N)]
for i in range(N-1):
    x, y = map(int, input().split())
    X[x-1].append(y-1)
    X[y-1].append(x-1)

P = [-1] * N
Q = deque([0])
R = []
while Q:
    i = deque.popleft(Q)
    R.append(i)
    for a in X[i]:
        if a != P[i]:
            P[a] = i
            X[a].remove(i)
            deque.append(Q, a)

# Settings Start
unit = [1 for i in range(K)]
merge = lambda a, b: [aa * bb % mod for aa, bb in zip(a, b)]
def adj_bu(a, i):
    b = a[:]
    for j in range(1, K):
        b[j] += b[j-1]
        b[j] %= mod
    return b
def adj_td(a, i, p):
    b = a[:]
    for j in range(1, K):
        b[j] += b[j-1]
        b[j] %= mod
    return b
def adj_td_unique(a, i, p):
    b = [0] + a[:-1]
    for j in range(1, K):
        b[j] += b[j-1]
        b[j] %= mod
    return b
def adj_fin(a, i):
    b = a[:]
    for j in range(1, K):
        b[j] += b[j-1]
        b[j] %= mod
    return b[-1]
# Settings End

ME = [unit] * N
XX = [0] * N
TD = [unit] * N
ANS = [0] * N
for i in R[1:][::-1]:
    XX[i] = adj_bu(ME[i], i)
    p = P[i]
    ME[p] = merge(ME[p], XX[i])
XX[R[0]] = adj_fin(ME[R[0]], R[0])
ANS[R[0]] = adj_fin(ME[R[0]], R[0])

for i in R:
    ac = TD[i]
    for j in X[i]:
        TD[j] = ac
        ac = merge(ac, XX[j])
    ac = unit
    for j in X[i][::-1]:
        TD[j] = merge(TD[j], ac)
        ANS[j] = adj_fin(merge(ME[j], adj_td_unique(TD[j], j, i)), j)
        TD[j] = adj_td(TD[j], j, i)
        ac = merge(ac, XX[j])

print(sum([a for a in ANS]) % mod)