Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict
from collections import deque
import sys
sys.setrecursionlimit(10**6)

N, K = map(int, input().split())
ab = defaultdict(list)
for i in range(N-1):
    a, b = map(int, input().split())
    ab[a-1].append(b-1)
    ab[b-1].append(a-1)

MOD = 10**9+7


def dfs(v, pv, n):
    k = K-1 if pv == -1 else K-2
    a = 1
    for u in ab[v]:
        if u != pv:
            a *= dfs(u, v, k)
            a %= MOD
            k -= 1
    return a*n % MOD


print(dfs(0, -1, K))


Fixed submission:
from collections import defaultdict
from collections import deque
import sys
sys.setrecursionlimit(10**6)

N, K = map(int, input().split())
ab = defaultdict(list)
for i in range(N-1):
    a, b = map(int, input().split())
    ab[a-1].append(b-1)
    ab[b-1].append(a-1)

MOD = 10**9+7


def dfs(v, pv, n):
    k = K-1 if pv == -1 else K-2
    a = 1
    for u in ab[v]:
        if u != pv:
            a *= dfs(u, v, k)
            a %= MOD
            k -= 1
    return a*n % MOD


print(dfs(0, -1, K))

Buggy python submission (verdict: Runtime Error):
from collections import defaultdict
from collections import deque

N, K = map(int, input().split())
ab = defaultdict(list)
for i in range(N-1):
    a, b = map(int, input().split())
    ab[a-1].append(b-1)
    ab[b-1].append(a-1)

MOD = 10**9+7


def dfs(v, pv, n):
    k = K-1 if pv == -1 else K-2
    a = 1
    for u in ab[v]:
        if u != pv:
            a *= dfs(u, v, k)
            a %= MOD
            k -= 1
    return a*n % MOD


print(dfs(0, -1, K))


Fixed submission:
from collections import defaultdict
from collections import deque
import sys
sys.setrecursionlimit(10**6)

N, K = map(int, input().split())
ab = defaultdict(list)
for i in range(N-1):
    a, b = map(int, input().split())
    ab[a-1].append(b-1)
    ab[b-1].append(a-1)

MOD = 10**9+7


def dfs(v, pv, n):
    k = K-1 if pv == -1 else K-2
    a = 1
    for u in ab[v]:
        if u != pv:
            a *= dfs(u, v, k)
            a %= MOD
            k -= 1
    return a*n % MOD


print(dfs(0, -1, K))

Buggy python submission (verdict: Runtime Error):
from collections import defaultdict
from collections import deque

N, K = map(int, input().split())
ab = defaultdict(list)
for i in range(N-1):
    a, b = map(int, input().split())
    ab[a-1].append(b-1)
    ab[b-1].append(a-1)

MOD = 10**9+7


def dfs(v, pv, n):
    k = K-1 if pv == -1 else K-2
    a = 1
    for u in ab[v]:
        if u != pv:
            a *= dfs(u, v, k)
            k -= 1
    return a*n % MOD


print(dfs(0, -1, K))


Fixed submission:
from collections import defaultdict
from collections import deque
import sys
sys.setrecursionlimit(10**6)

N, K = map(int, input().split())
ab = defaultdict(list)
for i in range(N-1):
    a, b = map(int, input().split())
    ab[a-1].append(b-1)
    ab[b-1].append(a-1)

MOD = 10**9+7


def dfs(v, pv, n):
    k = K-1 if pv == -1 else K-2
    a = 1
    for u in ab[v]:
        if u != pv:
            a *= dfs(u, v, k)
            a %= MOD
            k -= 1
    return a*n % MOD


print(dfs(0, -1, K))

Buggy python submission (verdict: Runtime Error):
from collections import defaultdict
from collections import deque

N, K = map(int, input().split())
ab = defaultdict(list)
for i in range(N-1):
    a, b = map(int, input().split())
    ab[a-1].append(b-1)
    ab[b-1].append(a-1)

MOD = 10**9+7


def dfs(v, pv, n):
    k = K-1 if pv == -1 else K-2
    a = 1
    for u in ab[v]:
        if u != pv:
            a *= dfs(u, v, k)
            k -= 1
    return a*n % MOD


print(dfs(0, -1, K))


Fixed submission:
from collections import defaultdict
from collections import deque
import sys
sys.setrecursionlimit(10**6)

N, K = map(int, input().split())
ab = defaultdict(list)
for i in range(N-1):
    a, b = map(int, input().split())
    ab[a-1].append(b-1)
    ab[b-1].append(a-1)

MOD = 10**9+7


def dfs(v, pv, n):
    k = K-1 if pv == -1 else K-2
    a = 1
    for u in ab[v]:
        if u != pv:
            a *= dfs(u, v, k)
            a %= MOD
            k -= 1
    return a*n % MOD


print(dfs(0, -1, K))