Buggy python submission (verdict: Runtime Error):
#!/usr/bin/env python3
import sys

YES = "Yes"  # type: str
NO = "No"  # type: str


def solve(H: int, W: int, s: "List[str]"):

    dx = [-1, 0, 1, 0]
    dy = [0, -1, 0, 1]

    for i in range(H):
        for j in range(W):
            if(s[i][j] == '#'):
                f = False
                for k in range(4):
                    iy = i+dy[k]
                    ix = j+dx[k]
                    if(0 <= iy < H and 0 <= ix < W and s[iy][ix] == '#'):
                        f = True
                if(f == False):
                    print(NO)
                    exit()
                
    print(YES)

    return


# Generated by 1.1.5 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    s = [next(tokens) for _ in range(W)]  # type: "List[str]"
    solve(H, W, s)

if __name__ == '__main__':
    main()


Fixed submission:
#!/usr/bin/env python3
import sys

YES = "Yes"  # type: str
NO = "No"  # type: str


def solve(H: int, W: int, s: "List[str]"):

    dx = [-1, 0, 1, 0]
    dy = [0, -1, 0, 1]

    for i in range(H):
        for j in range(W):
            if(s[i][j] == '#'):
                f = False
                for k in range(4):
                    iy = i+dy[k]
                    ix = j+dx[k]
                    if(0 <= iy < H and 0 <= ix < W and s[iy][ix] == '#'):
                        f = True
                if(f == False):
                    print(NO)
                    exit()
                
    print(YES)

    return


# Generated by 1.1.5 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    s = [next(tokens) for _ in range(H)]  # type: "List[str]"
    solve(H, W, s)

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
#!/usr/bin/env python3
import sys

YES = "Yes"  # type: str
NO = "No"  # type: str


def solve(H: int, W: int, s: "List[str]"):

    dx = [-1, 0, 1, 0]
    dy = [0, -1, 0, 1]

    for i in range(H):
        for j in range(W):
            if(s[i][j] == '#'):
                f = False
                for k in range(4):
                    iy = i+dy[k]
                    ix = j+dx[k]
                    if(0 <= iy < H and 0 <= ix < W and s[iy][ix] == '#'):
                        f = True
                if(not f):
                    print(NO)
                    exit()
                
    print(YES)

    return


# Generated by 1.1.5 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    s = [next(tokens) for _ in range(W)]  # type: "List[str]"
    solve(H, W, s)

if __name__ == '__main__':
    main()


Fixed submission:
#!/usr/bin/env python3
import sys

YES = "Yes"  # type: str
NO = "No"  # type: str


def solve(H: int, W: int, s: "List[str]"):

    dx = [-1, 0, 1, 0]
    dy = [0, -1, 0, 1]

    for i in range(H):
        for j in range(W):
            if(s[i][j] == '#'):
                f = False
                for k in range(4):
                    iy = i+dy[k]
                    ix = j+dx[k]
                    if(0 <= iy < H and 0 <= ix < W and s[iy][ix] == '#'):
                        f = True
                if(f == False):
                    print(NO)
                    exit()
                
    print(YES)

    return


# Generated by 1.1.5 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    s = [next(tokens) for _ in range(H)]  # type: "List[str]"
    solve(H, W, s)

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
#!/usr/bin/env python3
import sys

YES = "Yes"  # type: str
NO = "No"  # type: str


def solve(H: int, W: int, s: "List[str]"):

    dx = [-1, 0, 1, 0]
    dy = [0, -1, 0, 1]

    for i in range(H):
        for j in range(W):
            if(s[i][j] == '#'):
                f = False
                for k in range(4):
                    iy = i+dy[k]
                    ix = j+dx[k]
                    if(0 <= iy < H and 0 <= ix < W and s[iyw][ix] == '#'):
                        f = True
                if(not f):
                    print(NO)
                    exit()
                
    print(YES)

    return


# Generated by 1.1.5 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    s = [next(tokens) for _ in range(W)]  # type: "List[str]"
    solve(H, W, s)

if __name__ == '__main__':
    main()


Fixed submission:
#!/usr/bin/env python3
import sys

YES = "Yes"  # type: str
NO = "No"  # type: str


def solve(H: int, W: int, s: "List[str]"):

    dx = [-1, 0, 1, 0]
    dy = [0, -1, 0, 1]

    for i in range(H):
        for j in range(W):
            if(s[i][j] == '#'):
                f = False
                for k in range(4):
                    iy = i+dy[k]
                    ix = j+dx[k]
                    if(0 <= iy < H and 0 <= ix < W and s[iy][ix] == '#'):
                        f = True
                if(f == False):
                    print(NO)
                    exit()
                
    print(YES)

    return


# Generated by 1.1.5 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    s = [next(tokens) for _ in range(H)]  # type: "List[str]"
    solve(H, W, s)

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
#!/usr/bin/env python3
import sys

YES = "Yes"  # type: str
NO = "No"  # type: str


def solve(H: int, W: int, s: "List[str]"):

    dx = [-1, 0, 1, 0]
    dy = [0, -1, 0, 1]

    for i in range(H):
        for j in range(W):
            if(s[i][j] == '#'):
                f = False
                for k in range(4):
                    iy = i+dy[k]
                    ix = j+dx[k]
                    if(0 <= iy < H and 0 <= ix < W and s[iy][ix] == '#'):
                        f = True
                if(not f):
                    print(NO)
                    exit()
                
    print(YES)

    return


# Generated by 1.1.5 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    s = [next(tokens) for _ in range(W)]  # type: "List[str]"
    solve(H, W, s)

if __name__ == '__main__':
    main()


Fixed submission:
#!/usr/bin/env python3
import sys

YES = "Yes"  # type: str
NO = "No"  # type: str


def solve(H: int, W: int, s: "List[str]"):

    dx = [-1, 0, 1, 0]
    dy = [0, -1, 0, 1]

    for i in range(H):
        for j in range(W):
            if(s[i][j] == '#'):
                f = False
                for k in range(4):
                    iy = i+dy[k]
                    ix = j+dx[k]
                    if(0 <= iy < H and 0 <= ix < W and s[iy][ix] == '#'):
                        f = True
                if(f == False):
                    print(NO)
                    exit()
                
    print(YES)

    return


# Generated by 1.1.5 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    s = [next(tokens) for _ in range(H)]  # type: "List[str]"
    solve(H, W, s)

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
#!/usr/bin/env python3
import sys

YES = "Yes"  # type: str
NO = "No"  # type: str


def solve(H: int, W: int, s: "List[str]"):

    dx = [-1, 0, 1, 0]
    dy = [0, -1, 0, 1]

    for i in range(H):
        for j in range(W):
            if(s[i][j] == '#'):
                f = False
                for k in range(4):
                    iy = i+dx[k]
                    ix = j+dy[k]
                    if(0 <= iy < H and 0 <= ix < W and s[iy][ix] == '#'):
                        f = True
                if(not f):
                    print(NO)
                    exit()
                
    print(YES)

    return


# Generated by 1.1.5 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    s = [next(tokens) for _ in range(W)]  # type: "List[str]"
    solve(H, W, s)

if __name__ == '__main__':
    main()


Fixed submission:
#!/usr/bin/env python3
import sys

YES = "Yes"  # type: str
NO = "No"  # type: str


def solve(H: int, W: int, s: "List[str]"):

    dx = [-1, 0, 1, 0]
    dy = [0, -1, 0, 1]

    for i in range(H):
        for j in range(W):
            if(s[i][j] == '#'):
                f = False
                for k in range(4):
                    iy = i+dy[k]
                    ix = j+dx[k]
                    if(0 <= iy < H and 0 <= ix < W and s[iy][ix] == '#'):
                        f = True
                if(f == False):
                    print(NO)
                    exit()
                
    print(YES)

    return


# Generated by 1.1.5 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    H = int(next(tokens))  # type: int
    W = int(next(tokens))  # type: int
    s = [next(tokens) for _ in range(H)]  # type: "List[str]"
    solve(H, W, s)

if __name__ == '__main__':
    main()