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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def quantity(self, quantity):
 """ Sets the quantity of this OrderLineItem. The quantity purchased, as a string representation of a number. This string must have a positive integer value. :param quantity: The quantity of this OrderLineItem. :type: str """


        if quantity is None:
            raise ValueError("Invalid value for `quantity`, must not be `None`")
        if len(quantity) > 5:
            raise ValueError("Invalid value for `quantity`, length must be less than `5`")
        if len(quantity) < 1:
            raise ValueError("Invalid value for `quantity`, length must be greater than or equal to `1`")

        self._quantity = quantity