如何增加HashTable中的值？

class HashTable:
    def __init__(self):
        self.size = 10
        self.table = [None] * self.size

    def _hash(self, key):
        return hash(key) % self.size

    def insert(self, key, value):
        index = self._hash(key)
        if self.table[index] is None:
            self.table[index] = (key, value)
        elif self.table[index][0] == key:
            self.table[index] = (key, self.table[index][1] + value)
        else:
            while True:
                index = (index + 1) % self.size
                if self.table[index] is None:
                    self.table[index] = (key, value)
                    break
                elif self.table[index][0] == key:
                    self.table[index] = (key, self.table[index][1] + value)
                    break

    def get(self, key):
        index = self._hash(key)
        if self.table[index] is None:
            return None
        elif self.table[index][0] == key:
            return self.table[index][1]
        else:
            while True:
                index = (index + 1) % self.size
                if self.table[index] is None:
                    return None
                elif self.table[index][0] == key:
                    return self.table[index][1]