Return a list containing the names of the files in the directory.
path can be specified as either str, bytes, or a path-like object. If
path is bytes, the filenames returned will also be bytes; in all other
circumstances the filenames returned will be str.
If path is None, uses the path='.'.
On some platforms, path may also be specified as an open file
descriptor; the file descriptor must refer to a directory. If this
functionality is unavailable, using it raises NotImplementedError.
The list is in arbitrary order. It does not include the special
entries '.' and '..' even if they are present in the directory.