What is the significance of the deer dream image in poetry?

Liezi said: Zheng's men caught the deer, but left behind what they had hidden, so they thought it was a dream. Later generations used this code name to indicate that the world is like a dream. Fetters: instruments of torture, which refer to fetters and handcuffs. This is an ancient instrument of torture in China. It is worn on hands and feet. "Dream as a deer, die in chains" means that the world is unhappy and dreamy, leaving your heart in the shackles of spirit.