code: public SDVariable slice(String name, SDVariable input, int[] begin, int[] size) {
          SDVariable ret = f().slice(input, begin, size);
          return updateVariableNameAndReference(ret, name);
      }
docs: Get a subset of the specified input, by specifying the first element and the size of the array.<br>
  For example, if input is:<br>
  [a, b, c]<br>
  [d, e, f]<br>
  then slice(input, begin=[0,1], size=[2,1] will return:<br>
  [b]<br>
  [e]<br>
  <br>
  Note that for each dimension i, begin[i] + size[i] <= input.size(i)
  
  @param name  Output variable name
  @param input Variable to get subset of
  @param begin Beginning index. Must be same length as rank of input array
  @param size  Size of the output array. Must be same length as rank of input array
  @return Subset of the input