Return `True` if file or directory at `path` exist, False otherwise.

        Additional check on modified time when mtime is passed in.

        Return False if the file's modified time is older mtime.

def exists(self, path, mtime=None):
        """
        Return `True` if file or directory at `path` exist, False otherwise.

        Additional check on modified time when mtime is passed in.

        Return False if the file's modified time is older mtime.
        """
        self._connect()

        if self.sftp:
            exists = self._sftp_exists(path, mtime)
        else:
            exists = self._ftp_exists(path, mtime)

        self._close()

        return exists