Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(2147483647)

n,m=map(int,input().split())

#n,m<=10**5

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n
    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]
    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.parents[x] > self.parents[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x
    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

uf = UnionFind(m+1) #初期化

lastcheck=set([])
klkl=[]
for _ in range(n):
    kl=list(map(int,input().split()))[1:]
    if len(kl)>1:
        for item in kl[1:]:
            uf.union(kl[0]-1,item-1)
    klkl.append(kl)
uf_list=uf.members(item-1)    

flag=0
for kl in klkl:
    for item in kl:
        item-=1
        if item not in uf_list:
            flag=1
        else:
            break
if flag==1:
    print("NO")
else:
    print("YES")
    














Fixed submission:
import sys
sys.setrecursionlimit(2147483647)

n,m=map(int,input().split())

#n,m<=10**5

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n
    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]
    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.parents[x] > self.parents[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x
    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

uf = UnionFind(m+1) #初期化

lastcheck=set([])
klkl=[]
for _ in range(n):
    kl=list(map(int,input().split()))[1:]
    if len(kl)>1:
        for item in kl[1:]:
            uf.union(kl[0]-1,item-1)
    klkl.append(kl)
uf_list=uf.members(klkl[0][0]-1)
#print(uf_list)
flag=0
for kl in klkl:
    for item in kl:
        item-=1
        if item not in uf_list:
            flag=1
        else:
            break
if flag==1:
    print("NO")
else:
    print("YES")

Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(2147483647)

n,m=map(int,input().split())

#n,m<=10**5

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n
    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]
    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.parents[x] > self.parents[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x
    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

uf = UnionFind(m+1) #初期化

lastcheck=set([])
klkl=[]
for _ in range(n):
    kl=list(map(int,input().split()))[1:]
    if len(kl)==1:
        lastcheck.add(kl[0])
    else:
        for item in kl[1:]:
            uf.union(kl[0]-1,item-1)
    klkl.append(kl)
uf_list=uf.members(item-1)    

flag=0
for kl in klkl:
    for item in kl:
        item-=1
        if item not in uf_list:
            flag=1
        else:
            break
if flag==1:
    print("NO")
else:
    print("YES")
    














Fixed submission:
import sys
sys.setrecursionlimit(2147483647)

n,m=map(int,input().split())

#n,m<=10**5

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n
    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]
    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.parents[x] > self.parents[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x
    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

uf = UnionFind(m+1) #初期化

lastcheck=set([])
klkl=[]
for _ in range(n):
    kl=list(map(int,input().split()))[1:]
    if len(kl)>1:
        for item in kl[1:]:
            uf.union(kl[0]-1,item-1)
    klkl.append(kl)
uf_list=uf.members(klkl[0][0]-1)
#print(uf_list)
flag=0
for kl in klkl:
    for item in kl:
        item-=1
        if item not in uf_list:
            flag=1
        else:
            break
if flag==1:
    print("NO")
else:
    print("YES")

Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(2147483647)

n,m=map(int,input().split())

#n,m<=10**5

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n
    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]
    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.parents[x] > self.parents[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x
    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

uf = UnionFind(m+1) #初期化

lastcheck=set([])
klkl=[]
for _ in range(n):
    kl=list(map(int,input().split()))[1:]
    if len(kl)==1:
        lastcheck.add(kl[0])
    else:
        for item in kl[1:]:
            uf.union(kl[0]-1,item-1)
    klkl.append(kl)
uf_list=uf.members(item-1)    

flag=0
for kl in klkl:
    for item in kl:
        item-=1
        if item not in uf_list:
            flag=1
if flag==1:
    print("NO")
else:
    print("YES")
    














Fixed submission:
import sys
sys.setrecursionlimit(2147483647)

n,m=map(int,input().split())

#n,m<=10**5

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n
    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]
    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.parents[x] > self.parents[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x
    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

uf = UnionFind(m+1) #初期化

lastcheck=set([])
klkl=[]
for _ in range(n):
    kl=list(map(int,input().split()))[1:]
    if len(kl)>1:
        for item in kl[1:]:
            uf.union(kl[0]-1,item-1)
    klkl.append(kl)
uf_list=uf.members(klkl[0][0]-1)
#print(uf_list)
flag=0
for kl in klkl:
    for item in kl:
        item-=1
        if item not in uf_list:
            flag=1
        else:
            break
if flag==1:
    print("NO")
else:
    print("YES")

Buggy python submission (verdict: Runtime Error):
n,m=map(int,input().split())

#n,m<=10**5

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n
    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]
    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.parents[x] > self.parents[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x
    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

uf = UnionFind(m+1) #初期化

lastcheck=set([])
klkl=[]
for _ in range(n):
    kl=list(map(int,input().split()))[1:]
    if len(kl)==1:
        lastcheck.add(kl[0])
    else:
        for item in kl[1:]:
            uf.union(kl[0]-1,item-1)
    klkl.append(kl)
uf_list=uf.members(item-1)    

flag=0
for kl in klkl:
    for item in kl:
        item-=1
        if item not in uf_list:
            flag=1
if flag==1:
    print("NO")
else:
    print("YES")
    














Fixed submission:
import sys
sys.setrecursionlimit(2147483647)

n,m=map(int,input().split())

#n,m<=10**5

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n
    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]
    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.parents[x] > self.parents[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x
    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

uf = UnionFind(m+1) #初期化

lastcheck=set([])
klkl=[]
for _ in range(n):
    kl=list(map(int,input().split()))[1:]
    if len(kl)>1:
        for item in kl[1:]:
            uf.union(kl[0]-1,item-1)
    klkl.append(kl)
uf_list=uf.members(klkl[0][0]-1)
#print(uf_list)
flag=0
for kl in klkl:
    for item in kl:
        item-=1
        if item not in uf_list:
            flag=1
        else:
            break
if flag==1:
    print("NO")
else:
    print("YES")