KeError:Chair

[1xiaoxiaozhang]

Before posting an issue:

• Check here if anyone already posted the question
• Make sure you followed all steps in the README
• Choose a clear and appropriate title (remember: you don't have to paste the error code nor to write a too long title, only to sum it up). Do not use CAPS LOCK nor exclamation point.

Information to provide:

• If an error is encountered, the traceback
• If a new feature/information is request, be straightforward and complete