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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 is_valid(self):
 """ Validate for required parameters. """

        if not isinstance(self._expiration, datetime.datetime):
            raise InvalidArgumentError('Expiration datetime must be specified.')

        if 'key' not in self.form_data:
            raise InvalidArgumentError('object key must be specified.')

        if 'bucket' not in self.form_data:
            raise InvalidArgumentError('bucket name must be specified.')