Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(200000)

nl = lambda: list(map(int, input().split()))
sl = lambda: input().split()
n = lambda: int(input())
s = lambda: input()

N, K = nl()

from collections import defaultdict
edges = defaultdict(set)
for i in range(N-1):
    a, b = nl()
    edges[a].add(b)
    edges[b].add(a)


done = [False] * (N+1)
done[1] = True

def find(i, cands, prev):
    res = cands

    count = 0
    if prev:
        count += 1
    for edge in edges[i]:
        if done[edge]:
            continue
        count += 1
        done[edge] = True
        res *= find(edge, K - count, True)
        res %= 1000000007
    return res


print(find(1, K, False))



Fixed submission:
import sys
sys.setrecursionlimit(200000)

nl = lambda: list(map(int, input().split()))
sl = lambda: input().split()
n = lambda: int(input())
s = lambda: input()

N, K = nl()

from collections import defaultdict
edges = defaultdict(set)
for i in range(N-1):
    a, b = nl()
    edges[a].add(b)
    edges[b].add(a)


done = [False] * (N+1)
done[1] = True

def find(i, cands, prev):
    res = cands

    count = 0
    if prev:
        count += 1
    for edge in edges[i]:
        if done[edge]:
            continue
        count += 1
        done[edge] = True
        res *= find(edge, K - count, True)
        res %= 1000000007
    return res


print(find(1, K, False))

Buggy python submission (verdict: Runtime Error):

nl = lambda: list(map(int, input().split()))
sl = lambda: input().split()
n = lambda: int(input())
s = lambda: input()

N, K = nl()

from collections import defaultdict
edges = defaultdict(set)
for i in range(N-1):
    a, b = nl()
    edges[a].add(b)
    edges[b].add(a)


done = [False] * (N+1)
done[1] = True

def find(i, cands, prev):
    res = cands

    count = 0
    if prev:
        count += 1
    for edge in edges[i]:
        if done[edge]:
            continue
        count += 1
        done[edge] = True
        res *= find(edge, K - count, True)
        res %= 1000000007
    return res


print(find(1, K, False))



Fixed submission:
import sys
sys.setrecursionlimit(200000)

nl = lambda: list(map(int, input().split()))
sl = lambda: input().split()
n = lambda: int(input())
s = lambda: input()

N, K = nl()

from collections import defaultdict
edges = defaultdict(set)
for i in range(N-1):
    a, b = nl()
    edges[a].add(b)
    edges[b].add(a)


done = [False] * (N+1)
done[1] = True

def find(i, cands, prev):
    res = cands

    count = 0
    if prev:
        count += 1
    for edge in edges[i]:
        if done[edge]:
            continue
        count += 1
        done[edge] = True
        res *= find(edge, K - count, True)
        res %= 1000000007
    return res


print(find(1, K, False))

Buggy python submission (verdict: Runtime Error):

nl = lambda: list(map(int, input().split()))
sl = lambda: input().split()
n = lambda: int(input())
s = lambda: input()

N, K = nl()

from collections import defaultdict
edges = defaultdict(set)
for i in range(N-1):
    a, b = nl()
    edges[a].add(b)
    edges[b].add(a)


done = [False] * (N+1)
done[1] = True

def find(i, cands, prev):
    res = cands

    count = 0
    if prev:
        count += 1
    for edge in edges[i]:
        if done[edge]:
            continue
        count += 1
        done[edge] = True
        res *= find(edge, K - count, True)
    return res % 1000000007


print(find(1, K, False))



Fixed submission:
import sys
sys.setrecursionlimit(200000)

nl = lambda: list(map(int, input().split()))
sl = lambda: input().split()
n = lambda: int(input())
s = lambda: input()

N, K = nl()

from collections import defaultdict
edges = defaultdict(set)
for i in range(N-1):
    a, b = nl()
    edges[a].add(b)
    edges[b].add(a)


done = [False] * (N+1)
done[1] = True

def find(i, cands, prev):
    res = cands

    count = 0
    if prev:
        count += 1
    for edge in edges[i]:
        if done[edge]:
            continue
        count += 1
        done[edge] = True
        res *= find(edge, K - count, True)
        res %= 1000000007
    return res


print(find(1, K, False))

Buggy python submission (verdict: Runtime Error):

nl = lambda: list(map(int, input().split()))
sl = lambda: input().split()
n = lambda: int(input())
s = lambda: input()

N, K = nl()

from collections import defaultdict
edges = defaultdict(set)
for i in range(N-1):
    a, b = nl()
    edges[a].add(b)
    edges[b].add(a)


done = [False] * (N+1)
done[1] = True

def find(i, cands, prev):
    res = cands

    count = 0
    if prev:
        count += 1
    for edge in edges[i]:
        if done[edge]:
            continue
        count += 1
        done[edge] = True
        res *= find(edge, K - count, True)
    return res % 1000000007


print(find(1, K, False))



Fixed submission:
import sys
sys.setrecursionlimit(200000)

nl = lambda: list(map(int, input().split()))
sl = lambda: input().split()
n = lambda: int(input())
s = lambda: input()

N, K = nl()

from collections import defaultdict
edges = defaultdict(set)
for i in range(N-1):
    a, b = nl()
    edges[a].add(b)
    edges[b].add(a)


done = [False] * (N+1)
done[1] = True

def find(i, cands, prev):
    res = cands

    count = 0
    if prev:
        count += 1
    for edge in edges[i]:
        if done[edge]:
            continue
        count += 1
        done[edge] = True
        res *= find(edge, K - count, True)
        res %= 1000000007
    return res


print(find(1, K, False))