Update base_report.py

[cneskey]

FutureWarning about aggregation functions (np.mean, np.std, np.min, np.max): The warning suggests that in future versions of pandas, the callable will be used directly, so to maintain the current behavior, we should pass the string name of the aggregation function instead of the numpy function. from risk_results = risk_results.agg([np.mean, np.std, np.min, np.max]) to risk_results = risk_results.agg(['mean', 'std', 'min', 'max'])