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: VideoWriter.m
    path of file: ./repos/mexopencv/+cv
    
    the code of the file until where you have to start completion: classdef VideoWriter < handle
    %VIDEOWRITER  Video Writer class
    %
    % The class provides API for writing video files or image sequences.
    %
    % Note: When querying a property that is not supported by the backend
    % used by the cv.VideoWriter instance, v
    
function retval = isOpened(this)
            %ISOPENED  Returns true if video writer has been successfully initialized
            %
            %     retval = vid.isOpened()
            %
            % ## Output
            % * __val__ bool, return value
            %
            % Returns true if video writer has been successfully initialized.
            %
            % See also: cv.VideoWriter.open
            %
            retval = VideoWriter_(this.id, 'isOpened');
        end