a poker-faced expression的用法和样例：
- He wore a poker face during police questioning.
- She concealed her strong emotions behind a poker face.
- People with a “poker face”, whose emotions are hidden by a deadpan expression, are looked upon with suspicion.
- He maintains a poker face and you can't even guess what he's thinking.
- She came into the office with a poker face without greeting anybody.
- He seldom jokes around in the office; instead, he often keeps a poker face.