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

N = int(input())
MOD = 10 ** 9 + 7

to = [[] for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].append(y-1)
    to[y-1].append(x-1)

def dfs(n,p):
    w = 1
    b = 1
    for i in to[n]:
        if i != p:
            rw, rb = dfs(i, n)
            w *= (rw + rb)
            w %= MOD
            b *= rw
            b %= MOD
    return (w,b)

ans = dfs(0, -1)
print((ans[0] + ans[1]) % MOD)

Fixed submission:
import sys
sys.setrecursionlimit(200000)

N = int(input())
MOD = 10 ** 9 + 7

to = [[] for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].append(y-1)
    to[y-1].append(x-1)

def dfs(n,p):
    w = 1
    b = 1
    for i in to[n]:
        if i != p:
            rw, rb = dfs(i, n)
            w *= (rw + rb)
            w %= MOD
            b *= rw
            b %= MOD
    return (w,b)

ans = dfs(0, -1)
print((ans[0] + ans[1]) % MOD)

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

N = int(input())
MOD = 10 ** 9 + 7

to = [[] for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].append(y-1)
    to[y-1].append(x-1)

visited = [False] * N
def dfs(n):
    visited[n] = True
    w = 1
    b = 1
    for i in to[n]:
        if visited[i] == False:
            rw, rb = dfs(i)
            w *= (rw + rb) % MOD
            b *= rw % MOD
    return (w,b)

ans = dfs(0)
print((ans[0] + ans[1]) % MOD)

Fixed submission:
import sys
sys.setrecursionlimit(200000)

N = int(input())
MOD = 10 ** 9 + 7

to = [[] for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].append(y-1)
    to[y-1].append(x-1)

def dfs(n,p):
    w = 1
    b = 1
    for i in to[n]:
        if i != p:
            rw, rb = dfs(i, n)
            w *= (rw + rb)
            w %= MOD
            b *= rw
            b %= MOD
    return (w,b)

ans = dfs(0, -1)
print((ans[0] + ans[1]) % MOD)

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

N = int(input())
MOD = 10 ** 9 + 7

to = [set() for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].add(y-1)
    to[y-1].add(x-1)

visited = [False] * N
def dfs(n):
    visited[n] = True
    w = 1
    b = 1
    for i in to[n]:
        if visited[i] == False:
            rw, rb = dfs(i)
            w *= rw + rb
            b *= rw
    w %= MOD
    b %= MOD
    return (w,b)

ans = dfs(0)
print((ans[0] + ans[1]) % MOD)

Fixed submission:
import sys
sys.setrecursionlimit(200000)

N = int(input())
MOD = 10 ** 9 + 7

to = [[] for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].append(y-1)
    to[y-1].append(x-1)

def dfs(n,p):
    w = 1
    b = 1
    for i in to[n]:
        if i != p:
            rw, rb = dfs(i, n)
            w *= (rw + rb)
            w %= MOD
            b *= rw
            b %= MOD
    return (w,b)

ans = dfs(0, -1)
print((ans[0] + ans[1]) % MOD)

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

N = int(input())
MOD = 10 ** 9 + 7

to = [[] for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].append(y-1)
    to[y-1].append(x-1)

visited = [False] * N
def dfs(n):
    visited[n] = True
    w = 1
    b = 1
    for i in to[n]:
        if visited[i] == False:
            rw, rb = dfs(i)
            w *= rw + rb
            b *= rw
    w %= MOD
    b %= MOD
    return (w,b)

ans = dfs(0)
print((ans[0] + ans[1]) % MOD)

Fixed submission:
import sys
sys.setrecursionlimit(200000)

N = int(input())
MOD = 10 ** 9 + 7

to = [[] for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].append(y-1)
    to[y-1].append(x-1)

def dfs(n,p):
    w = 1
    b = 1
    for i in to[n]:
        if i != p:
            rw, rb = dfs(i, n)
            w *= (rw + rb)
            w %= MOD
            b *= rw
            b %= MOD
    return (w,b)

ans = dfs(0, -1)
print((ans[0] + ans[1]) % MOD)

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

N = int(input())
MOD = 10 ** 9 + 7

root = {i for i in range(N)}

to = [[] for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].append(y-1)
    to[y-1].append(x-1)

visited = [False] * N
def dfs(n):
    visited[n] = True
    w = 1
    b = 1
    for i in to[n]:
        if visited[i] == False:
            rw, rb = dfs(i)
            w *= rw + rb
            b *= rw
    w %= MOD
    b %= MOD
    return [w,b]

ans = dfs(0)
print((ans[0] + ans[1]) % MOD)

Fixed submission:
import sys
sys.setrecursionlimit(200000)

N = int(input())
MOD = 10 ** 9 + 7

to = [[] for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].append(y-1)
    to[y-1].append(x-1)

def dfs(n,p):
    w = 1
    b = 1
    for i in to[n]:
        if i != p:
            rw, rb = dfs(i, n)
            w *= (rw + rb)
            w %= MOD
            b *= rw
            b %= MOD
    return (w,b)

ans = dfs(0, -1)
print((ans[0] + ans[1]) % MOD)

Buggy python submission (verdict: Runtime Error):
N = int(input())

root = {i for i in range(N)}

to = [[] for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].append(y-1)
    to[y-1].append(x-1)

visited = [False] * N
def dfs(n):
    visited[n] = True
    w = 1
    b = 1
    for i in to[n]:
        if visited[i] == False:
            rw, rb = dfs(i)
            w *= rw + rb
            b *= rw
    return [w,b]

ans = dfs(0)
print(ans[0] + ans[1])

Fixed submission:
import sys
sys.setrecursionlimit(200000)

N = int(input())
MOD = 10 ** 9 + 7

to = [[] for _ in range(N)]
for _ in range(N-1):
    x, y = map(int, input().split())
    to[x-1].append(y-1)
    to[y-1].append(x-1)

def dfs(n,p):
    w = 1
    b = 1
    for i in to[n]:
        if i != p:
            rw, rb = dfs(i, n)
            w *= (rw + rb)
            w %= MOD
            b *= rw
            b %= MOD
    return (w,b)

ans = dfs(0, -1)
print((ans[0] + ans[1]) % MOD)