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: segymat.m
    path of file: ./repos/segymat/GUI
    
    the code of the file until where you have to start completion: function varargout = segymat(varargin)
% segymat : Garphical User Interface for SegyMAT
%
%   (C) 2001-2004 Thomas Mejer Hansen, tmh@gfy.ku.dk/thomas@cultpenguin.com
%
 

% SEGYMAT M-file for segymat.fig
%      SEGYMAT, by itself, creates a new SEGYMAT or raises the existing
%      singleton*.
%
%      H = SEGYMAT returns the handle to a new SEGYMAT or the handle to
%      the existing singleton*.
%
%      SEGYMAT('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in SEGYMAT.M with the given input arguments.
    
function mplot_Callback(hObject, eventdata, handles)
% hObject    handle to mplot (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)




% --------------------------------------------------------------------
function mEditTextualHeader_Callback(hObject, eventdata, handles)
% hObject    handle to mEditTextualHeader (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
data=guidata(hObject);
try
	data.SegyHeader=GUIEditTextualFileHeader(data.SegyHeader);
	guidata(hObject,data)
catch
end