Copy content of multiple files into a single file.

    :param list(str) sources: source file names (paths)
    :param str destination: destination file name (path)
    :return:

def merge_files(sources, destination):
    """Copy content of multiple files into a single file.

    :param list(str) sources: source file names (paths)
    :param str destination: destination file name (path)
    :return:
    """

    with open(destination, 'w') as hout:
        for f in sources:
            if os.path.exists(f):
                with open(f) as hin:
                    shutil.copyfileobj(hin, hout)
            else:
                logger.warning('File is missing: {}'.format(f))