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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 experiments_predictions_create(self, experiment_id, model_id, argument_defs, name, arguments=None, properties=None):
 """Create new model run for given experiment. Parameters experiment_id : string Unique experiment identifier model_id : string Unique identifier of model to run name : string User-provided name for the model run argument_defs : list(attribute.AttributeDefinition) Definition of valid arguments for the given model List of attribute instances properties : Dictionary, optional Set of model run properties. Returns ------- ModelRunHandle Handle for created model run or None if experiment is unknown """

        # Get experiment to ensure that it exists
        if self.experiments_get(experiment_id) is None:
            return None
        # Return created model run
        return self.predictions.create_object(
            name,
            experiment_id,
            model_id,
            argument_defs,
            arguments=arguments,
            properties=properties
        )