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: vl_ertr.m
    path of file: ./repos/Image-Harmonization-Dataset-iHarmony4/Lalonde and Efros/utilsPrivate/3rd_party/vlfeat-0.9.14/toolbox/mser
    
    the code of the file until where you have to start completion: function f = vl_ertr(f) ;
% VL_ERTR  Transpose exremal regions frames
%  F = VL_ERTR(F) transposes the frames F as returned by VL_MSER(). This
%  conversion is required as the VL_MSER algorithm considers the column
%  index I as the frist image index, while according standard image
%  convention the first coordinate is the abscissa X.

    
function f = vl_ertr(f) ;
% VL_ERTR  Transpose exremal regions frames
%  F = VL_ERTR(F) transposes the frames F as returned by VL_MSER(). This
%  conversion is required as the VL_MSER algorithm considers the column
%  index I as the frist image index, while according standard image
%  convention the first coordinate is the abscissa X.
%
%  See also: VL_MSER(), VL_HELP().

if size(f,1) ~= 5
  error('F is not in the right format') ;
end