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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 unwrap(self, value, fields=None, session=None):
        ''' Validate ``value`` and then use the document's class to unwrap the
            value'''
        self.validate_unwrap(value, fields=fields, session=session)
        return self.type.unwrap(value, fields=fields, session=session)