balanced brackets python

# Program to check balanced brackets using stack
test = int(input())
flag = False
for k in range(test):
    stack = []
    flag = False
    string = input()
    for i in string:
        if i == '{' or i=='(' or i=='[':
            stack.append(i)
        elif i == ')':
            if len(stack)>0:
                element = stack.pop()
                if element != '(':
                    flag = True
                    break
            else:
                flag = True
                break

        elif i == ']':
            if len(stack) > 0:
                element = stack.pop()
                if element != '[':
                    flag = True
                    break
            else:
                flag = True
                break

        elif i == '}':
            if len(stack) > 0:
                element = stack.pop()
                if element != '{':
                    flag = True
                    break
            else:
                flag = True
                break

    if not flag and len(stack) == 0:
        print("YES")
    else:
        print("NO")

'''

Sample Input

3
{[()]}
{[(])}
{{[[(())]]}}


Sample Output

YES
NO
YES
'''