docs: function _isDirectory (directory, callback) {
  
  			if ("undefined" === typeof directory) {
  				throw new ReferenceError("missing \"directory\" argument");
  			}
  				else if ("string" !== typeof directory) {
  					throw new TypeError("\"directory\" argument is not a string");
  				}
  				else if ("" === directory.trim()) {
  					throw new Error("\"directory\" argument is empty");
  				}
  			else if ("undefined" === typeof callback) {
  				throw new ReferenceError("missing \"callback\" argument");
  			}
  				else if ("function" !== typeof callback) {
  					throw new TypeError("\"callback\" argument is not a function");
  				}
  			else {
  
  				lstat(directory, (err, stats) => {
  					return callback(null, Boolean(!err && stats.isDirectory()));
  				});
  
  			}
  
  		}