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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 valueFromString(self, value, context=None):
 """ Re-implements the orb.Column.valueFromString method to lookup a reference object based on the given value. :param value: <str> :param context: <orb.Context> || None :return: <orb.Model> || None """

        model = self.referenceModel()
        return model(value, context=context)