Multiply Strings LeetCode solution in Python

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class Solution:
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    def multiply(self, num1: str, num2: str) -> str:
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        def convertToInt(numStr):
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            currNum = 0
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            N = len(numStr)
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            for i in range(N - 1, -1, -1):
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                digit = ord(numStr[i]) - ord("0")
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                currNum += pow(10, N - i - 1) * digit
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            return currNum
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        n1 = convertToInt(num1)
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        n2 = convertToInt(num2)
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        return str(n1 * n2)