Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
p = 10**9+7
def pow(X,k):
    if k==0:
        return np.eye(X.shape[0])
    if k==1:
        return X
    if k%2==0:
        return np.dot(pow(X,k//2),pow(X,k//2))%p
    else:
        return np.dot(X,np.dot(pow(X,(k-1)//2),pow(X,(k-1)//2))%p)%p
N,K = map(int,input().split())
A = np.zeros((N,N))
for i in range(N):
    a = np.array(list(map(int,input().split())))
    A[i][:] = a[:]
X = pow(A,K)
cnt = 0
for i in range(N):
    for j in range(N):
        cnt = (cnt+X[i][j])%p
print(int(cnt))

Fixed submission:
p = 10**9+7
def pow(X,k):
    if k==0:
        return [[1 if i==j else 0 for j in range(N)] for i in range(N)]
    if k==1:
        return X
    if k%2==0:
        Y = pow(X,k//2)
        Z = [[0 for _ in range(N)] for _ in range(N)]
        for i in range(N):
            for j in range(N):
                for m in range(N):
                    Z[i][j] = (Z[i][j]+Y[i][m]*Y[m][j])%p
        return Z
    else:
        Y = pow(X,(k-1)//2)
        Z = [[0 for _ in range(N)] for _ in range(N)]
        for i in range(N):
            for j in range(N):
                for m in range(N):
                    Z[i][j] = (Z[i][j]+Y[i][m]*Y[m][j])%p
        Z1 = [[0 for _ in range(N)] for _ in range(N)]
        for i in range(N):
            for j in range(N):
                for m in range(N):
                    Z1[i][j] = (Z1[i][j]+Z[i][m]*X[m][j])%p
        return Z1
N,K = map(int,input().split())
A = [list(map(int,input().split())) for _ in range(N)]
X = pow(A,K)
cnt = 0
for i in range(N):
    for j in range(N):
        cnt = (cnt+X[i][j])%p
print(int(cnt))

Buggy python submission (verdict: Runtime Error):
import numpy as np
p = 10**9+7
def pow(X,k):
    if k==0:
        return np.eye(X.shape[0])
    if k==1:
        return X
    if k%2==0:
        return np.dot(pow(X,k//2),pow(X,k//2))%p
    else:
        return np.dot(X,np.dot(pow(X,(k-1)//2),pow(X,(k-1)//2))%p)%p
N,K = map(int,input().split())
A = np.zeros((N,N))
for i in range(N):
    a = np.array(list(map(int,input().split())))
    A[i][:] = a[:]
X = pow(A,K)
cnt = 0
for i in range(N):
    for j in range(N):
        cnt = (cnt+X[i][j])%p
print(int(cnt))

Fixed submission:
p = 10**9+7
def pow(X,k):
    if k==0:
        return [[1 if i==j else 0 for j in range(N)] for i in range(N)]
    if k==1:
        return X
    if k%2==0:
        Y = pow(X,k//2)
        Z = [[0 for _ in range(N)] for _ in range(N)]
        for i in range(N):
            for j in range(N):
                for m in range(N):
                    Z[i][j] = (Z[i][j]+Y[i][m]*Y[m][j])%p
        return Z
    else:
        Y = pow(X,(k-1)//2)
        Z = [[0 for _ in range(N)] for _ in range(N)]
        for i in range(N):
            for j in range(N):
                for m in range(N):
                    Z[i][j] = (Z[i][j]+Y[i][m]*Y[m][j])%p
        Z1 = [[0 for _ in range(N)] for _ in range(N)]
        for i in range(N):
            for j in range(N):
                for m in range(N):
                    Z1[i][j] = (Z1[i][j]+Z[i][m]*X[m][j])%p
        return Z1
N,K = map(int,input().split())
A = [list(map(int,input().split())) for _ in range(N)]
X = pow(A,K)
cnt = 0
for i in range(N):
    for j in range(N):
        cnt = (cnt+X[i][j])%p
print(int(cnt))