in packages/docpack-markdown-extractor/lib/plugin.js [17:25]
init: function() {
var files = this.config.files;
if (files === null) {
this.emitError('`files` option should be provided');
} else if (typeof files != 'string' && !Array.isArray(files)) {
this.emitError('`files` can be a string (glob wildcard) or array of files');
}
}