Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a mediocre cop movie directed by and starring Clint Eastwood. He plays a drunk and undistinguished Phoenix cop named Ben who is given a death-sentence assignment by the corrupt police commissioner Blalock because nobody will miss him if he dies. His assignment is to fly to Las Vegas, pick up a witness named Gus, and bring her back to a mob trial in Phoenix. But the mob and an army of Las Vegas and Phoenix police officers under Blalock's orders all try to kill them before they get to the courthouse. By my count, more bullets are fired at them in this movie than were fired in every movie ever made, but they all miss!
On the road to Phoenix, after surviving bombs and hailstorms of bullets, they stop for the night at a large cave in the desert. They have a fight and she tells him she's going to leave him and take her chances on her own in the desert. He scares her into staying by telling her to watch out for sidewinder rattlesnakes.
The next morning, a gang of bikers rides up to Gus and Ben's hiding place. Ben grabs his gun, shows his badge, and threatens to arrest all of the bikers if they don't leave immediately. We see shots of one of the bikers, a woman, holding a California Kingsnake in her hand. It's just a snake cameo, but the snake is deliberately shown to us in a semi-close-up. I read on IMDB that while they were shooting in Nevada, Eastwood found a California Kingsnake and showed it to his co-star and girlfriend Sondra Locke who screamed in fear then eventually got used to it. Eastwood released the snake, but I wonder if he used the snake in the biker scene before letting it go, or if possibly the kingsnake he found inspired him to get another one to use in the movie. It's also possible that other scenes with the kingsnake were cut out of the movie.
The biker woman has another scene later, but it's not snake-related.
Ben and Gus hop a freight train to get away from the police, where they find some of the bikers whose motorcycles he destroyed. The bikers attack them. After he beats the men and throws them out of the car, the woman, who is not holding the snake this time, says to him "you wouldn't hit a lady" then he immediately punches her in the face forcing her out of the boxcar.