How to use the gcsfs.core.GCSFileSystem.tokens function in gcsfs

def _save_tokens():
        try:
            with open(tfile, 'wb') as f:
                pickle.dump(GCSFileSystem.tokens, f, 2)
        except Exception as e:
            warnings.warn('Saving token cache failed: ' + str(e))

def load_tokens():
        """Get "browser" tokens from disc"""
        try:
            with open(tfile, 'rb') as f:
                tokens = pickle.load(f)
            # backwards compatability
            tokens = {k: (GCSFileSystem._dict_to_credentials(v)
                          if isinstance(v, dict) else v)
                      for k, v in tokens.items()}
        except Exception:
            tokens = {}
        GCSFileSystem.tokens = tokens

def _save_tokens():
        try:
            with open(tfile, "wb") as f:
                pickle.dump(GCSFileSystem.tokens, f, 2)
        except Exception as e:
            warnings.warn("Saving token cache failed: " + str(e))

def load_tokens(cls):
        """Get "browser" tokens from disc"""
        try:
            with open(tfile, "rb") as f:
                tokens = pickle.load(f)
        except Exception:
            tokens = {}
        GCSFileSystem.tokens = tokens