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: Sum.m
    path of file: ./repos/TADT/utils/matconvnet/matlab/+dagnn
    
    the code of the file until where you have to start completion: classdef Sum < dagnn.ElementWise
  %SUM DagNN sum layer
  %   The SUM layer takes the sum of all its inputs and store the result

    
function rfs = getReceptiveFields(obj)
      numInputs = numel(obj.net.layers(obj.layerIndex).inputs) ;
      rfs.size = [1 1] ;
      rfs.stride = [1 1] ;
      rfs.offset = [1 1] ;
      rfs = repmat(rfs, numInputs, 1) ;
    end