You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: DagNN.m
    path of file: ./repos/TADT/utils/matconvnet/matlab/+dagnn/@DagNN
    
    the code of the file until where you have to start completion: classdef DagNN < matlab.mixin.Copyable
%DagNN Directed acyclic graph neural network
%   DagNN is a CNN wrapper alternative to SimpleNN. It is object
%   oriented and allows constructing networks with a directed acyclic
%   graph (DAG
    
function setParameterServer(obj, ps)
    %SETPARAMETERSERVER  Set a parameter server for the parameter derivatives
    %    SETPARAMETERSERVER(obj, PS) uses the specified
    %    ParameterServer PS to store and accumulate parameter
    %    derivatives across multiple MATLAB processes.
    %
    %    After setting this option, net.params.der is always empty
    %    and the derivative value must be retrieved from the
    %    server.

      obj.parameterServer = ps ;
      for p = 1:numel(obj.params)
        if strcmp(class(obj.params(p).value),'gpuArray')
          deviceType = 'gpu' ;
          dataType = classUnderlying(obj.params(p).value) ;
        else
          deviceType = 'cpu' ;
          dataType = class(obj.params(p).value) ;
        end