code: def create(self, params):
          
          sh_id = params.get('id', str(uuid4()))
          if sh_id in self:
              raise ShardedClusterError(
                  "Sharded cluster with id %s already exists." % sh_id)
          params['id'] = sh_id
          cluster = ShardedCluster(params)
          self[cluster.id] = cluster
          return cluster.id
docs: create new ShardedCluster
          Args:
             params - dictionary with specific params for instance
          Return cluster_id
             where cluster_id - id which can use to take the cluster from servers collection