code: public SDVariable argmax(SDVariable in, int... dimensions) {
          return argmax(null, in, false, dimensions);
      }
docs: Argmax array reduction operation, optionally along specified dimensions.<br>
  Output values are the index of the maximum value of each slice along the specified dimension
  
  @param in         Input variable
  @param dimensions Dimensions to reduce over. If dimensions are not specified, full array reduction is performed
  @return Reduced array of rank (input rank - num dimensions)