Set value to key-value
        Params:
            <str> key
            <int> value
            <int> key_length
        Return:
            <int> key_value

def set(self, key, value, key_length=0):
        """Set value to key-value
        Params:
            <str> key
            <int> value
            <int> key_length
        Return:
            <int> key_value
        """
        if key_length < 1:
            key_length = len(key)
        if self.k:
            self._update(key, value)
        return self.set_method(self, key, key_length, value)