Buggy python submission (verdict: Time Limit Exceeded):
# 末端の頂点は白1通り、黒1通り
# それ以外の頂点は、各子どもの頂点を元に、白:子の全ての場合分けの積、黒:子が全て白の場合分けの積
# で更新していく

N = int(input())
G = [set() for i in range(N)]
MOD = 10 ** 9 + 7

for i in range(N - 1):
  x,y = map(int,input().split())
  G[x - 1].add(y - 1)
  G[y - 1].add(x - 1)
  
dp_black = [-1] * N
dp_white = [-1] * N

stack = [-1,0]

while len(stack) > 1:
  v = stack[-1]
  parent = stack[-2]
  black = 1
  white = 1
  for child in G[v]:
    if child == parent:
      continue
    if dp_black[child] == -1:
      stack.append(child)
      break
    black *= dp_white[child]
    black %= MOD
    white *= (dp_black[child] + dp_white[child])
    white %= MOD
  else:
    dp_black[v] = black
    dp_white[v] = white
    stack.pop()
    
print((dp_black[0] + dp_white[0]) % MOD)    


Fixed submission:
import sys
sys.setrecursionlimit(10 ** 6)

# 末端の頂点は白1通り、黒1通り
# それ以外の頂点は、各子どもの頂点を元に、白:子の全ての場合分けの積、黒:子が全て白の場合分けの積
# で更新していく

N = int(input())
G = [[] for i in range(N)]
MOD = 10 ** 9 + 7

for i in range(N - 1):
  x,y = map(int,input().split())
  G[x - 1].append(y - 1)
  G[y - 1].append(x - 1)
  
dp_black = [-1] * N
dp_white = [-1] * N

# 頂点vの(黒,白)の場合の数を求める
def search(v,parent):
  if dp_black[v] != -1:
    return (dp_black[v],dp_white[v])
  black = 1
  white = 1
  for child in G[v]:
    if child == parent:
      continue
    b,w = search(child, v)
    black *= w
    black %= MOD
    white *= (b + w)
    white %= MOD
  dp_black[v] = black
  dp_white[v] = white
  return (black, white)

print(sum(search(0, -1)) % MOD)

Buggy python submission (verdict: Time Limit Exceeded):
# 末端の頂点は白1通り、黒1通り
# それ以外の頂点は、各子どもの頂点を元に、白:子の全ての場合分けの積、黒:子が全て白の場合分けの積
# で更新していく

N = int(input())
G = [set() for i in range(N)]
MOD = 10 ** 9 + 7

for i in range(N - 1):
  x,y = map(int,input().split())
  G[x - 1].add(y - 1)
  G[y - 1].add(x - 1)
  
dp_black = [-1] * N
dp_white = [-1] * N

stack = [-1,0]

while len(stack) > 1:
  v = stack[-1]
  parent = stack[-2]
  black = 1
  white = 1
  for child in G[v]:
    if child == parent:
      continue
    if dp_black[child] == -1:
      stack.append(child)
      break
    black *= dp_white[child]
    black %= MOD
    white *= (dp_black[child] + dp_white[child])
    white %= MOD
  else:
    dp_black[v] = black
    dp_white[v] = white
    stack.pop()
    
print((dp_black[0] + dp_white[0]) % MOD)    


Fixed submission:
import sys
sys.setrecursionlimit(10 ** 6)

# 末端の頂点は白1通り、黒1通り
# それ以外の頂点は、各子どもの頂点を元に、白:子の全ての場合分けの積、黒:子が全て白の場合分けの積
# で更新していく

N = int(input())
G = [[] for i in range(N)]
MOD = 10 ** 9 + 7

for i in range(N - 1):
  x,y = map(int,input().split())
  G[x - 1].append(y - 1)
  G[y - 1].append(x - 1)
  
dp_black = [-1] * N
dp_white = [-1] * N

# 頂点vの(黒,白)の場合の数を求める
def search(v,parent):
  if dp_black[v] != -1:
    return (dp_black[v],dp_white[v])
  black = 1
  white = 1
  for child in G[v]:
    if child == parent:
      continue
    b,w = search(child, v)
    black *= w
    black %= MOD
    white *= (b + w)
    white %= MOD
  dp_black[v] = black
  dp_white[v] = white
  return (black, white)

print(sum(search(0, -1)) % MOD)

Buggy python submission (verdict: Runtime Error):
# 末端の頂点は白1通り、黒1通り
# それ以外の頂点は、各子どもの頂点を元に、白:子の全ての場合分けの積、黒:子が全て白の場合分けの積
# で更新していく

N = int(input())
G = [[] for i in range(N)]
MOD = 10 ** 9 + 7

for i in range(N - 1):
  x,y = map(int,input().split())
  G[x - 1].append(y - 1)
  G[y - 1].append(x - 1)
  
dp_black = [-1] * N
dp_white = [-1] * N

# 頂点vの(黒,白)の場合の数を求める
def search(v,parent):
  if dp_black[v] != -1:
    return (dp_black[v],dp_white[v])
  black = 1
  white = 1
  for child in G[v]:
    if child == parent:
      continue
    b,w = search(child, v)
    black *= w
    black %= MOD
    white *= (b + w)
    white %= MOD
  dp_black[v] = black
  dp_white[v] = white
  return (black, white)

print(sum(search(0, -1)) % MOD)


Fixed submission:
import sys
sys.setrecursionlimit(10 ** 6)

# 末端の頂点は白1通り、黒1通り
# それ以外の頂点は、各子どもの頂点を元に、白:子の全ての場合分けの積、黒:子が全て白の場合分けの積
# で更新していく

N = int(input())
G = [[] for i in range(N)]
MOD = 10 ** 9 + 7

for i in range(N - 1):
  x,y = map(int,input().split())
  G[x - 1].append(y - 1)
  G[y - 1].append(x - 1)
  
dp_black = [-1] * N
dp_white = [-1] * N

# 頂点vの(黒,白)の場合の数を求める
def search(v,parent):
  if dp_black[v] != -1:
    return (dp_black[v],dp_white[v])
  black = 1
  white = 1
  for child in G[v]:
    if child == parent:
      continue
    b,w = search(child, v)
    black *= w
    black %= MOD
    white *= (b + w)
    white %= MOD
  dp_black[v] = black
  dp_white[v] = white
  return (black, white)

print(sum(search(0, -1)) % MOD)