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: subsref.m
    path of file: ./repos/fieldtrip/external/spm8/@nifti
    
    the code of the file until where you have to start completion: function varargout = subsref(opt,subs)
% Subscript referencing
%
% Fields are:
% dat         - a file-array representing the image data
% mat0        - a  9-parameter affine transform (from qform0)
%               Note that the mapping is from voxels (where the first
%               is considered to be at [1,1,1], to millimetres.  See
%               mat0_interp for the meaning of the transform.
% mat         - a 12-parameter affine transform (from sform0)
%               Note that the mapping is from voxels (where the first
%               is considered to be at [1,1,1], to millimetres.  See
%               mat1_interp for the meaning of the transform.
% mat_intent  - intention of mat.  This field may be missing/empty.
% mat0_intent - intention of mat0. This field may be missing/empty.
% intent      - interpretation of image. When present, this structure
%               contains the fields
%               code   - name of interpretation

    
function varargout = subsref(opt,subs)
% Subscript referencing
%
% Fields are:
% dat         - a file-array representing the image data
% mat0        - a  9-parameter affine transform (from qform0)
%               Note that the mapping is from voxels (where the first
%               is considered to be at [1,1,1], to millimetres.  See
%               mat0_interp for the meaning of the transform.
% mat         - a 12-parameter affine transform (from sform0)
%               Note that the mapping is from voxels (where the first
%               is considered to be at [1,1,1], to millimetres.  See
%               mat1_interp for the meaning of the transform.
% mat_intent  - intention of mat.  This field may be missing/empty.
% mat0_intent - intention of mat0. This field may be missing/empty.
% intent      - interpretation of image. When present, this structure
%               contains the fields
%               code   - name of interpretation
%               params - parameters needed to interpret the image
% diminfo     - MR encoding of different dimensions.  This structure may
%               contain some or all of the following fields
%               frequency  - a value of 1-3 indicating frequency direction
%               phase      - a value of 1-3 indicating phase direction
%               slice      - a value of 1-3 indicating slice direction
%               slice_time - only present when "slice" field is present.
%                            Contains the following fields
%                            code     - ascend