Return a `~paramiko.sftp_client.SFTPClient` object.

        If called more than one time, memoizes the first result; thus, any
        given `.Connection` instance will only ever have a single SFTP client,
        and state (such as that managed by
        `~paramiko.sftp_client.SFTPClient.chdir`) will be preserved.

        .. versionadded:: 2.0

def sftp(self):
        """
        Return a `~paramiko.sftp_client.SFTPClient` object.

        If called more than one time, memoizes the first result; thus, any
        given `.Connection` instance will only ever have a single SFTP client,
        and state (such as that managed by
        `~paramiko.sftp_client.SFTPClient.chdir`) will be preserved.

        .. versionadded:: 2.0
        """
        if self._sftp is None:
            self._sftp = self.client.open_sftp()
        return self._sftp