Aggregators

General Aggregators 

`Mean`	Computes the `sample mean` over the updates from all give clients.
`Median`	A robust aggregator from paper "Byzantine-robust distributed learning: Towards optimal statistical rates".
`Trimmedmean`	A robust aggregator from paper "Byzantine-robust distributed learning: Towards optimal statistical rates"
`GeoMed`	A robust aggregator from paper "Distributed Statistical Machine Learning in Adversarial Settings: Byzantine Gradient Descent".
`DnC`	A robust aggregator from paper "Manipulating the Byzantine: Optimizing Model Poisoning Attacks and Defenses for Federated Learning".
`Clippedclustering`	A robust aggregator from paper "An Experimental Study of Byzantine-Robust Aggregation Schemes in Federated Learning".
`Signguard`	A robust aggregator from paper "SignGuard: Byzantine-robust Federated Learning through Collaborative Malicious Gradient Filtering".
`Multikrum`	A robust aggregator from paper "Machine Learning with Adversaries: Byzantine Tolerant Gradient Descent".
`Centeredclipping`	A robust aggregator from the "Learning from History for Byzantine Robust Optimization" paper.