Final answer:
The provided context does not explicitly mention a signal for a cobra being in the room. Maybelle signals the arrival of police with her red bandana, and Dr. Steven Zucker speaks of a cobra as a symbol of royalty.
Step-by-step explanation:
In the context provided, the signal that a cobra is in the room is not explicitly mentioned. Instead, we have information about a different event, where Maybelle indicates the arrival of police by changing the position of her red bandana. However, in an example related to invisibility and symbolism, Dr. Steven Zucker mentions that a cobra, the insignia of royalty, might be placed somewhere to denote a royal presence. If a cobra was indeed the topic of discussion, the removal of the cobra insignia would symbolize the change in status of the once-royal figure.
As for Maybelle's signal, when the red bandana is seen in her front pocket, the folks dancing quickly switched partners so they were no longer dancing in same-sex pairs, but rather in male/female couples, just as the police arrive. The quick change served as a precautionary response to potential police raids in a time when same-sex dancing might have been illegal or socially unacceptable.