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: ismatrix.m
    path of file: ./repos/fieldtrip/compat/matlablt2010b
    
    the code of the file until where you have to start completion: function [varargout] = ismatrix(varargin)

% ISMATRIX is a 
    
function tf = ismatrix(x)

% deal with the input arguments
if nargin==1
  [x] = deal(varargin{1:1});
else
  error('incorrect number of input arguments')
end