Buggy python submission (verdict: Time Limit Exceeded):
# @author 

import sys


class PIndependentSet:
    def solve(self):
        from collections import defaultdict
        import sys
        sys.setrecursionlimit(10 ** 5 + 5)
        MOD = 10 ** 9 + 7

        def dfs(s):
            done[s] = 1
            dp[s][0] = 1
            dp[s][1] = 1
            for x in adj[s]:
                if done[x]:
                    continue
                dfs(x)
                dp[s][0] = (dp[s][0] * dp[x][1]) % MOD
                dp[s][1] = (dp[s][1] * (dp[x][0] + dp[x][1])) % MOD

        n = int(input())
        adj = defaultdict(list)

        for i in range(n - 1):
            x, y = [int(_) for _ in input().split()]
            x -= 1
            y -= 1
            adj[x].append(y)
            adj[y].append(x)

        dp = [[0, 0] for _ in range(n)]
        done = [0] * n
        dfs(0)

        print((dp[0][0] + dp[0][1]) % MOD)

solver = PIndependentSet()
input = sys.stdin.readline

solver.solve()


Fixed submission:
# @author 

import sys


class PIndependentSet:
    def solve(self):
        from collections import defaultdict
        import sys
        sys.setrecursionlimit(10 ** 5 + 5)
        MOD = 10 ** 9 + 7

        def dfs(s):
            done[s] = 1
            dp[s][0] = 1
            dp[s][1] = 1
            for x in adj[s]:
                if done[x]:
                    continue
                dfs(x)
                dp[s][0] = (dp[s][0] * dp[x][1]) % MOD
                dp[s][1] = (dp[s][1] * (dp[x][0] + dp[x][1])) % MOD

        n = int(input())
        adj = defaultdict(list)

        for i in range(n - 1):
            x, y = [int(_) for _ in input().split()]
            x -= 1
            y -= 1
            adj[x].append(y)
            adj[y].append(x)

        dp = [[0, 0] for _ in range(n)]
        done = [0] * n
        dfs(0)

        print((dp[0][0] + dp[0][1]) % MOD)

solver = PIndependentSet()
input = sys.stdin.readline

solver.solve()

Buggy python submission (verdict: Runtime Error):
# @author 

import sys


class PIndependentSet:
    def solve(self):
        from collections import defaultdict

        MOD = 10 ** 9 + 7

        def dfs(s):
            done[s] = 1
            dp[s][0] = 1
            dp[s][1] = 1
            for x in adj[s]:
                if done[x]:
                    continue
                _in = True
                dfs(x)
                dp[s][0] = (dp[s][0] * dp[x][1]) % MOD
                dp[s][1] = (dp[s][1] * (dp[x][0] + dp[x][1])) % MOD

        n = int(input())
        adj = defaultdict(list)

        for i in range(n - 1):
            x, y = [int(_) for _ in input().split()]
            x -= 1
            y -= 1
            adj[x].append(y)
            adj[y].append(x)

        dp = [[0, 0] for _ in range(n)]
        done = [0] * n
        dfs(0)

        print(dp[0][0] + dp[0][1])

solver = PIndependentSet()
input = sys.stdin.readline

solver.solve()


Fixed submission:
# @author 

import sys


class PIndependentSet:
    def solve(self):
        from collections import defaultdict
        import sys
        sys.setrecursionlimit(10 ** 5 + 5)
        MOD = 10 ** 9 + 7

        def dfs(s):
            done[s] = 1
            dp[s][0] = 1
            dp[s][1] = 1
            for x in adj[s]:
                if done[x]:
                    continue
                dfs(x)
                dp[s][0] = (dp[s][0] * dp[x][1]) % MOD
                dp[s][1] = (dp[s][1] * (dp[x][0] + dp[x][1])) % MOD

        n = int(input())
        adj = defaultdict(list)

        for i in range(n - 1):
            x, y = [int(_) for _ in input().split()]
            x -= 1
            y -= 1
            adj[x].append(y)
            adj[y].append(x)

        dp = [[0, 0] for _ in range(n)]
        done = [0] * n
        dfs(0)

        print((dp[0][0] + dp[0][1]) % MOD)

solver = PIndependentSet()
input = sys.stdin.readline

solver.solve()